Fix for #2 - Including some feature adds and cleanup

Hi There,

This is in response to #2.  The root of the issue was `fail_silently` was not used and was not flagging any issues when there was issues.  The second change was a bit more evasive.

  - Added in more validations in line with Flowdocks API
  - Further added in more fail_silently catches
  - PEP-8 / Future-proofing / Housekeeping

Added in several new Features.
  - Ability to use a customer from_address (default Django is not valid)
  - Set a minimum threshold to send notifications to Flowdock
  - Optionally set the tags values to push to Flowdock as tags.
     - For example if you set "version" it will push the corresponding version value to Flowdock as a tag.
 
This is replaced by Rules and we're not wanting plugins to specify this kind of behavior anymore.