Updated Data Scrubbing

:warning: Still need to write tests

Issue #9 

Updated the data scrubbing code to allow for users to include their own custom processors. It also validates against a few more "bad keys" such as "authorization", "apikey", and "api_key." I took these keys from [raven-python](https://github.com/getsentry/raven-python/blob/b7fc2128bc9eee0897883fe25a8efa459c85e9af/raven/processors.py#L63)

I also added value validation to scrub out anything that looks like a credit card number.
Also it's now scrubbing HTTP Headers.


This is a more thorough implementation of: http://sentry.readthedocs.org/en/latest/developer/client/#scrubbing-data