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
Codeception test adjustments for basic and advanced applications

- Moved everything test-related into `tests` directory. Codeception tests are in `codeception`.
- Removed database module since we're using fixtures and migrations.
- Moved console entry points and bootstrap into `tests/codeception/bin`.
- Adjusted travis build scripts.
- Adjusted documentation to be consistent and reflect changes made.
Merge branch 'master' into codeception-test-adjustments

Conflicts:
	.travis.yml
Fixed templates and fixtures paths for advanced application