Event handling functionality separated out into module.
More examples in demo for event handling and over 15 objects.

- Added codePen example link in README.
- Events can now use this keyword to specify that current object.
This fixes #2 - Prevent dragging after mouseup or dragend event.
JS optimizations.

- For in loops for arrays are now regular for loops.
- Mousemove event listener only listening to canvas element instead of window.