Exception Filters

As I’ve announced in issue #679 I was going to add a feature for filtering errors on Errbit’s side. This is included in this PR to share with you guys. There is a separate page which allows users to create filters on two levels: global and application. When an exception gets send to Errbit it passes through the global filters and those coupled on an application. The filters let you write Regular Expressions to give you more control over the matching, also I’ve included a Rake task for running the filters on the current database of errors and set all that don’t pass the filters to resolved. The reason for this feature is that our applications are producing some exceptions that we don't want. These applications are old and we aren't going through all of them to add filters on the application side. That's why we want to filter them out in Errbit. I love to hear feedback on this and if you want to merge this 😉. I tried to keep changes to the current codebase to a minimum and added tests for all the changes I did. (P.S. sorry for the long list of commits. I'm taught to commit small things all the time.)