updated changelog about isEmpty bug.

fix tabs

fix tabs

Guide not found links

fixed some urls in guide; moved elasticsearch png file to proper location, to be seen by apidoc generator

Fixes Yii1 reference.

Update test-fixture.md

small typo

Added advanced app tests to travis

Tests codestyle fix

Code style fixes

this term is resolveable by the php docs when linking types in apidoc

Update HttpBearerAuth.php

typo fix

* 'master' of github.com:yiisoft/yii2:
  Make code coverage work
  Note about  embedded documents added to mongodb extension readme
  yii\mongodb\file\Collection::ensureMongoId() fixed to suppress exception on invalid _id format.
  yii\mongodb\file\ActiveRecord::update() fixed to save the attributes while updating file.
  Fixes #2661: Added boolean column type support for SQLite
  Refactored controller creation process.
  Added back some toArray() implementations.
  Fixed test break.
  Update console-migrate.md
  Fixes #2655: Arrayable and ArrayableTrait are incompatible for some PHP versions.
  Fixes #2659
  Minor code style fixes for apidoc
  Changed assertions
  fix tests