Improve json_handler decorator

It will now sanely respond with a 405 error if the method is not POST or
a 400 error if the input is invalid. A wrapped function can now indicate
by raising a certain exception that a status code other than 200 or 500
should be returned.
Correctly count the number of pylint violations
Fix pylint errors; dummy var regex
report total pylint violations regardless
Merge pull request #216 from singingwolfboy/db/fix-pylint-script

Correctly count the number of pylint violations
Merge pull request #211 from edx/gprice/improve-json-handler

Improve json_handler decorator
Relax open_local_resource rules.

An XBlock developer couldn't figure out why his static files weren't
serving.  At the very least, dots in the filename should be ok.