Remove the dependency on ActiveSupport

ActiveSupport (particularly the core extensions) can play havoc with otherwise well-written applications that were not developed using ActiveSupport.  Since Honeybadger claims support for non-Rails frameworks, it makes little sense to include ActiveSupport and potentially cause those applications to fail.

For my own project, including Honeybadger caused a number of seemingly unrelated failures to occur, including URIs being serialized to JSON as Hash instances, and breaking DateTime comparisons against Integers.