TSAnimatedAdapter is used when rendering GIFs. TSAnimatedAdapter
inherits from JSQMediaItem but does not provide a custom implementation
of the hash method. The default implementation of hash in JSQMediaItem
results in all messages of a given interaction type (incoming,
outgoing) sharing a cached bubble size. For this reason, JSQMediaItem
subclasses are required to implement hash (see
https://github.com/jessesquires/JSQMessagesViewController/issues/631).
This commit fixes issue #1275 by implementing hash in TSAnimatedAdapter
the same way TSPhotoAdapter does.