Add webhook handler
Fix: Exception string whitespace and formatting
Ignore *.egg files
Remove: Signal trigger on HEAD request
Raise exception if not using webhook secret
Fix: webhook view post method

Gets the JSON data from the mandrill_events param.
Also returns a 400 error if there's any issues
loading the webhook request.
Add: tests for webhook mixin and view
Merge pull request #33 from jpadilla/webhooks

Webhooks