fixes #52
Merge branch 'master' of github.com:LaxarJS/JSON-Patch into merge-pull-request-53

Conflicts:
	src/json-patch-duplex.js.map
add unit and performance test for "compare" operation
move applying of chages to mirror outside of _generate function.
code cleanup effect: jsonpatch.generate now uses jsonpatch.apply instead of custom code to propagate changes to the mirror

In Chrome 46% performance increase for "jsonpatch.compare" and 2% performance decrease for "jsonpatch.generate".
In Firefox, 65% performance increase for "jsonpatch.compare" and and 6% performance decrease for "jsonpatch.generate".