[FIX] Whitespace typo in README.md
[!!!][API] Add Layer class

An image can contain several layers.
Handlers are applied on layers.
A layer is an independent pixel matrix.
Image now extend EventEmitter, to emit several useful events (such as changeSize).
[API] Allow layers access using readonly property, make add/remove private
[FIX] Remove log statement from Layer tests
[API] Add reset() method to Image
[FIX] Fix wrong UID test on Layer
[!!!] [API] Remove shorthand syntaxes, add matrix property

Use explicit handler using (with handler() method)
Reduce dependency on Harmony features (but still have on .matrix property)
[!!!] [API] Rename .use to .import for more consistency
[TASK] Use identifiers in object keys, with es5 flag
[TASK] Use strict mode
[!!!][API] Change .handler to more consistent .run
[TASK] Update README.md with 11 last commits
[TASK] Update package.json
[FIX] Fix typo in Layer test suite