Merge branch 'master' of github.com:yiisoft/yii2 into email-swift-2
Interface 'MailerInterface' extracted.
Method 'MailerInterface::createMessage()' added.
'yii\mail\ViewResolve' removed.
Interface 'ViewContextInterface' applied to BaseMailer.
moved common parts of db ActiveRelation and Query to traits

these parts can be reused in other ActiveRecord implementations
add relationClassName to AR to allow different relation classes

... for different dbms
fixed conflicting property declaration
'yii\mail\MessageInterface' file related methods interface adjusted to use options, embed file methods added.
skip expiry test for memcache on travis

fixes #877
print travis ENV
travis memcache env check: try again
simplified travis env check for memcache(d)
'yii\mail\MessageInterface' methods 'addText()' and 'addHtml()' removed.
set error_reporting for tests
Email message charset setup added.
Merge branch 'master' of github.com:yiisoft/yii2 into email-swift-2
made gridview plural rule compatible with ICU version < 4.8

issue #1072
added unit test to verify storing of null values

http://www.yiiframework.com/forum/index.php/topic/48359-inserting-nulls/page__view__findpost__p__226019
fixed unit tests for cubrid and postgresql

both do not support unsigned integers
refactored Component::off().
Fixes #1025: Implemented support for class-level events.