Mask shadow layer in LFSTextField

Also add some comments and a TODO.
Default to empty string when userToken is nil
Save unnecessary bootstrap requests

When we already have content, lookup the latest event ID
and start streaming from it, without querying bootstrap server
again.

Also, clear comment box on either “Post” or “Cancel”, to reduce
chances of same content being posted twice (in case of “Post”)
and to save user time (in case of “Cancel”).
Merge pull request #4 from Livefyre/dev

Dev