Add weakset functionality
Add gitignore, replace builder with closurecompiler

Closurecompiler gives the maximum possible compression
Rename build to dist

Dist is considered as a more common practice for placing bundles
Replace tests with mocha

Mocha allows to debug things the way better: it is able to turn on/off
specific tests and shows the lines of code where errors took place
Refactor code

Replace `Object.create`s with prototypal shared methods - it is
considered to be hundreds of times faster
http://jsperf.com/object-create-method-vs-prototype-method.

Move all polyfill-related tasks out.

Reduce clutter and optimize code for closurecompiler.
Add testling settings