Improved force add

Force add now works even if deltabot has already replied. It will not
give a delta if it's already confirmed one, but it will remove any other
comments and re-add them. There is a way to edit instead of delete/add,
but I couldn't get it to work. This should be improved in the future for
aesthetic purposes.

This code assumes that the confirmation message always starts with the
same first 15 characters.
Merge pull request #28 from PixelOrange/master

Improved force add