Tabs to spaces to be consistent

```
vendor/bin/indent --spaces -r framework/
vendor/bin/indent --tabs -r . --pattern=*.json
vendor/bin/indent --spaces -r . --pattern=*.md
vendor/bin/indent --spaces -r . --pattern=yii.*.js
vendor/bin/indent --spaces -r . --pattern=*.css
```

composer.json

@@ -1,29 +1,29 @@
 {
-    "name": "yiisoft/yii2-bootstrap",
-    "description": "The Twitter Bootstrap extension for the Yii framework",
-    "keywords": ["yii2", "bootstrap"],
-    "type": "yii2-extension",
-    "license": "BSD-3-Clause",
-    "support": {
-        "issues": "https://github.com/yiisoft/yii2/issues?labels=ext%3Abootstrap",
-        "forum": "http://www.yiiframework.com/forum/",
-        "wiki": "http://www.yiiframework.com/wiki/",
-        "irc": "irc://irc.freenode.net/yii",
-        "source": "https://github.com/yiisoft/yii2"
-    },
-    "authors": [
-        {
-            "name": "Qiang Xue",
-            "email": "qiang.xue@gmail.com"
-        }
-    ],
-    "require": {
-        "yiisoft/yii2": "*",
-        "twbs/bootstrap": "3.1.* | 3.0.*"
-    },
-    "autoload": {
-        "psr-4": {
-            "yii\\bootstrap\\": ""
-        }
-    }
+	"name": "yiisoft/yii2-bootstrap",
+	"description": "The Twitter Bootstrap extension for the Yii framework",
+	"keywords": ["yii2", "bootstrap"],
+	"type": "yii2-extension",
+	"license": "BSD-3-Clause",
+	"support": {
+		"issues": "https://github.com/yiisoft/yii2/issues?labels=ext%3Abootstrap",
+		"forum": "http://www.yiiframework.com/forum/",
+		"wiki": "http://www.yiiframework.com/wiki/",
+		"irc": "irc://irc.freenode.net/yii",
+		"source": "https://github.com/yiisoft/yii2"
+	},
+	"authors": [
+		{
+			"name": "Qiang Xue",
+			"email": "qiang.xue@gmail.com"
+		}
+	],
+	"require": {
+		"yiisoft/yii2": "*",
+		"twbs/bootstrap": "3.1.* | 3.0.*"
+	},
+	"autoload": {
+		"psr-4": {
+			"yii\\bootstrap\\": ""
+		}
+	}
 }