Fix for #4372
Doc update [skip ci]
Changelog update [skip ci]
Merge with master
Update .gitignore
Update .gitignore
Fixes #4636: Added `yii\web\Response::setDownloadHeaders()`
Fixes #4501: Renamed the constant `YII_PATH` to `YII2_PATH`
added bower.json for yii2-framework. [skip ci]
updated ignore. [skip ci]
adjust bower.json further [skip ci]
do not export mailer in BaseMailerTest message

fixes test break in HHVM due to export of a closure
fixed some inconsistnecies in HHVM tests

exclude parts that have different default values
more on HHVM compatibility
skip application tests on HHVM
HHVM version ouput has changed
fixed HHVM test break
Added bower.json for gii and debug extensions.
Update structure-widgets.md

changed bootstrap namespace to jui
Merge pull request #4726 from xskif/patch-1

[skip-ci] Update structure-widgets.md