Change mutator modifier from `__prop_` to `$$prop$$`

`__mutate_fn : function() {}` => `$$mutate$$fn : function() {}`
Updating native regexp and speed up keys lookup
Optimize create polyfill
Exporting utility functions to the Classify object
Non breaking change to allow for adding multiple prop mutators
Unit tests for multiple prop mutators
Fix lint error
BREAKING CHANGE: mutator prefix is always removed
Allow for greedy onPropRemove mutators and allow multiple mutators in onPropRemove
Unit tests for multi onPropRemove
Unit tests for greedy mutators
Remove unused comments
Pass matched mutators to onPropAdd
Merge pull request #10 from weikinhuang/multi-mutator

BREAKING CHANGES: Adding ability to call multiple mutators on a single property