Restructured i18n doc, finished i18n formatter section

docs/guide/i18n.md

@@ -45,8 +45,10 @@ If there's no translation for `ru-RU` Yii will try `ru` as well before failing.
 > **Note**: you can further customize details specifying language
 > [as documented in ICU project](http://userguide.icu-project.org/locale#TOC-The-Locale-Concept).
 
-Basic message translation
--------------------------
+Message translation
+-------------------
+
+### Basics
 
 Yii basic message translation in its basic variant works without additional PHP extension. What it does is finding a
 translation of the message from source language into target language. Message itself is specified as the second
@@ -97,7 +99,7 @@ language is used.
 
 Instead of configuring `fileMap` you can rely on convention which is `messages/BasePath/LanguageID/CategoryName.php`.
 
-### Named placeholders
+#### Named placeholders
 
 You can add parameters to a translation message that will be substituted with the corresponding value after translation.
 The format for this is to use curly brackets around the parameter name as you can see in the following example:
@@ -111,7 +113,7 @@ echo \Yii::t('app', 'Hello, {username}!', [
 
 Note that the parameter assignment is without the brackets.
 
-### Positional placeholders
+#### Positional placeholders
 
 ```php
 $sum = 42;
@@ -121,8 +123,8 @@ echo \Yii::t('app', 'Balance: {0}', $sum);
 > **Tip**: Try keep message strings meaningful and avoid using too many positional parameters. Remember that
 > translator has source string only so it should be obvious about what will replace each placeholder.
 
-Advanced placeholder formatting
--------------------------------
+### Advanced placeholder formatting
+
 
 In order to use advanced features you need to install and enable [intl](http://www.php.net/manual/en/intro.intl.php) PHP
 extension. After installing and enabling it you will be able to use extended syntax for placeholders. Either short form
@@ -132,7 +134,7 @@ that allows you to specify formatting style.
 Full reference is [available at ICU website](http://icu-project.org/apiref/icu4c/classMessageFormat.html) but since it's
 a bit cryptic we have our own reference below.
 
-### Numbers
+#### Numbers
 
 ```php
 $sum = 42;
@@ -155,7 +157,7 @@ echo \Yii::t('app', 'Balance: {0, number, ,000,000000}', $sum);
 
 [Formatting reference](http://icu-project.org/apiref/icu4c/classicu_1_1DecimalFormat.html).
 
-### Dates
+#### Dates
 
 ```php
 echo \Yii::t('app', 'Today is {0, date}', time());
@@ -175,7 +177,7 @@ echo \Yii::t('app', 'Today is {0, date, YYYY-MM-dd}', time());
 
 [Formatting reference](http://icu-project.org/apiref/icu4c/classicu_1_1SimpleDateFormat.html).
 
-### Time
+#### Time
 
 ```php
 echo \Yii::t('app', 'It is {0, time}', time());
@@ -196,13 +198,13 @@ echo \Yii::t('app', 'It is {0, date, HH:mm}', time());
 [Formatting reference](http://icu-project.org/apiref/icu4c/classicu_1_1SimpleDateFormat.html).
 
 
-### Spellout
+#### Spellout
 
 ```php
 echo \Yii::t('app', '{n,number} is spelled as {n, spellout}', ['n' => 42]);
 ```
 
-### Ordinal
+#### Ordinal
 
 ```php
 echo \Yii::t('app', 'You are {n, ordinal} visitor here!', ['n' => 42]);
@@ -210,7 +212,7 @@ echo \Yii::t('app', 'You are {n, ordinal} visitor here!', ['n' => 42]);
 
 Will produce "You are 42nd visitor here!".
 
-### Duration
+#### Duration
 
 
 ```php
@@ -219,7 +221,7 @@ echo \Yii::t('app', 'You are here for {n, duration} already!', ['n' => 47]);
 
 Will produce "You are here for 47 sec. already!".
 
-### Plurals
+#### Plurals
 
 Different languages have different ways to inflect plurals. Some rules are very complex so it's very handy that this
 functionality is provided without the need to specify inflection rule. Instead it only requires your input of inflected
@@ -251,7 +253,7 @@ Total {count, number} {count, plural, one{item} other{items}}.
 To learn which inflection forms you should specify for your language you can referrer to
 [rules reference at unicode.org](http://unicode.org/repos/cldr-tmp/trunk/diff/supplemental/language_plural_rules.html).
 
-### Selections
+#### Selections
 
 You can select phrases based on keywords. The pattern in this case specifies how to map keywords to phrases and
 provides a default phrase.
@@ -268,25 +270,6 @@ Will produce "Snoopy is dog and it loves Yii!".
 In the expression `female` and `male` are possible values. `other` handler values that do not match. Strings inside
 brackets are sub-expressions so could be just a string or a string with more placeholders.
 
-Views
------
-
-You can use i18n in your views to provide support for different languages. For example, if you have view `views/site/index.php` and
-you want to create special case for russian language, you create `ru-RU` folder under the view path of current controller/widget and
-put there file for russian language as follows `views/site/ru-RU/index.php`.
-
-> **Note**: If language is specified as `en-US` and there are no corresponding views, Yii will try views under `en`
-> before using original ones.
-
-Formatters
-----------
-
-In order to use formatters you need to install and enable [intl](http://www.php.net/manual/en/intro.intl.php) PHP
-extension.
-
-Examples
---------
-
 ### Specifying default translation
 
 You can specify default translation that will be used as a fallback for categories that don't match any other translation.
@@ -410,4 +393,36 @@ Instead of using `fileMap` you can simply use convention of category mapping to
 
 > **Note**: For widgets you also can use i18n views, same rules as for controllers are applied to them too.
 
-TBD: provided classes overview.
+Views
+-----
+
+You can use i18n in your views to provide support for different languages. For example, if you have view `views/site/index.php` and
+you want to create special case for russian language, you create `ru-RU` folder under the view path of current controller/widget and
+put there file for russian language as follows `views/site/ru-RU/index.php`.
+
+> **Note**: If language is specified as `en-US` and there are no corresponding views, Yii will try views under `en`
+> before using original ones.
+
+i18n formatter
+--------------
+
+i18n formatter component is the localized version of formatter that supports formatting of date, time and numbers based
+on current locale. In order to use it you need to configure formatter application component as follows:
+
+```php
+return [
+	// ...
+	'components' => [
+		'formatter' => [
+			'class' => 'yii\i18n\Formatter',
+		],
+	],
+];
+```
+
+After cofiguring the component can be accessed as `Yii::$app->formatter`.
+
+Note that in order to use i18n formatter you need to install and enable
+[intl](http://www.php.net/manual/en/intro.intl.php) PHP extension.
+
+In order to learn about formatter methods refer to its API documentation: [[yii\i18n\Formatter]].