Merge pull request #1 from Coeuvre/master

Moved code from `piston`
Merge pull request #2 from Coeuvre/master

Added more ease functions
Merge pull request #3 from Coeuvre/master

Added a gif image for demonstration
Merge pull request #4 from Coeuvre/master

Now we can pause, resume or toggle the actions
Merge pull request #5 from Coeuvre/master

Added `remove_child` to `Scene`
Upgraded to latest piston-event
Merge pull request #11 from bvssvni/master

Upgraded to latest piston-event
Store state in behavior tree

Closes https://github.com/PistonDevelopers/sprite/issues/12
Merge pull request #13 from bvssvni/master

Store state in behavior tree
Updated the dependencies link