add handler property to yii\web\Session
simpler implementation of the handler property in yii\web\Session
Redundant event's instanceof check

And some docs punctuation.
Merge pull request #1769 from crtlib/patch-3

Redundant event's instanceof check and some docs punctuation
fix template guide, twig section
updated docs of Event
allow class level trigger call on Event subclasses

e.g. UserEvent::trigger('event', 'class');
should result in a UserEvent to be passed to the handlers instead of
a base\Event.
simple fix for #1747
Merge pull request #1770 from yupe/master

fix template guide twig section
another small fix for debug toolbar

issue #1747
updatd TwigRenderer docs, closes #1771
refactored debug toolbar assets

also fixed problems with display on small screens.

fixes #1747
made debug toolbar position fixed again

issue #1747
CHANGELOG line for #1747
removed hard restriction of cache keyPrefix to alnum

fixes #1773
CHANGELOG for #1773
try to fix basic app travis.yml
FixtureController code style fixes and typo fixes
Merge pull request #1774 from creocoder/fixture-controller-code-style-fixes

FixtureController code style fixes and typo fixes
Update migration.md

dots do not work.