Merge branch 'gh-pages'
- Added CollsionManager to load
- Change width and height to private properties and added getters and setters for them
- CollisionManager class
- Transfer responsability for collisions to collisionmanager
- Adjustments in width and height of the _collisionsurface creation inside the Collisionmanager class
- Added original width and height properties to sprite class
- Recalculate scaleX and scaleY of a Sprite when change his width and height
- Added module and tests to sprite class in tests.js
- Added module and tests to surface class in tests.js
- Some engine tests
- Refactor in ScaleX, scaleY, width and height
- Added some tests to suite
- Added image with a transparent background
- Added flag to sprite.boxColides to enable pixel collision
- Remove unused method from Sprite class
- Added pixel perfect collision detection
- Added debug constant
- Remove tests from Core
- Skip a added child if it's already in the list in Scene class
- Added method to scene class to remove a child by index