Updated README

Merge pull request yohang#38 from kovertopz/1.0

PHP 5.3 does not support indirect method calls with arrays or short arra...

Added unit test for Twig extension can method

Added an event on first state machine initialization

Merge pull request yohang#24 from dannykopping/patch-1

Fixing callbacks in example

Deprecated the StateInterface::can() method

Bumped docs and updated README