Update description of $httpBackend.respond(...)

For the novice, the previous description was not helpful. I hope this is more so.
The output of this creates one really long line right now, which causes UI problems with the app. @petebacondarwin is there a better way to format this? That would have to be addressed before this could be merged.

Aside from that, I think we should only use "res"+ and "req"+ instead of full names, and only in areas where the argument is ambiguous. `requestMethod`, `url` can stay as is, `data` in the fn signature can be `reqData`, .