Improve HipChat integration

I would like to use HipChat to automatically display notifications to the team when there are new pull requests, etc. so that any interested parties can have a look.

I'm trying to get the team to stop adding everyone as a reviewer and only invite one or two people but this is quite difficult when people feel they have little visibility (or awareness) of pull requests. And trying to get people to manually post a message about a pull request doesn't work reliably either!

There is another HipChat plugin on the marketplace (Go2Group) but it is all-or-nothing when it comes to pull requests: you get a notification for a new pull request (in fact you get two notifications for this and one has an invalid link), comments, adding commits (called rescoping), and merging (which in turn rescopes all other open pull request and they all send a notification). Basically, it needs to be more fine grained to avoid people ignoring them as overload.

I'd also like to have it "mention" people when their comment is replied to (or when their pull request is commented on). Ideally, I'd like to be able to stop email notifications and get the same kind of thing in HipChat.