switched to 'asset-packagist.org'

.travis.yml

@@ -14,7 +14,6 @@ cache:
 
 install:
   - travis_retry composer self-update && composer --version
-  - travis_retry composer global require "fxp/composer-asset-plugin:^1.2.0"
   - export PATH="$HOME/.composer/vendor/bin:$PATH"
   - travis_retry composer install --prefer-dist --no-interaction
 

composer.json

@@ -21,6 +21,12 @@
         "yiisoft/yii2": "~2.0.4",
         "swiftmailer/swiftmailer": "~6.0"
     },
+    "repositories": [
+        {
+            "type": "composer",
+            "url": "https://asset-packagist.org"
+        }
+    ],
     "autoload": {
         "psr-4": { "yii\\swiftmailer\\": "" }
     },