Adds mentions to reader comment replies

Turns out this covers both if you transition first into a particular post to reply AND for replies directly from the reader.
Yep - in this case the even simpler thing to do was add the suggestions view to the existing NSMutableDictionary, similar to how the replytextview is added.  Took care of this in https://github.com/wordpress-mobile/WordPress-iOS/commit/570b6f6ccf4137b985438fb8b459b7b172ec62be

Let me know if you'd still rather me switch to NSDictionaryOfVariableBindings