Add delete content functionality

Note: this breaks direct call compatibility with RC1 of v0.2.

Also make “postMessage” method more generic, supporting not only likes/unlikes,
but also deletes, bozo and other moderator-level functions.

Add a test to verify that delete action returns HTTP 200 and a JSON
object that has the same content id as the one being deleted.
rename user -> userToken whenever appropriate
Bump up to RC3
Support deletion of author content

This fixes a mistake in enum strings made in the previous few commits.
Further changes supporting deletion of content

In LFSWriteClient check that critical parameters are not nil.

In LFSCollectionViewController (sample app project), support editing only if user token is set.
Add “pending delete” state to visibility content enum

This allows us to display special text such as “this comment is being removed”
while the request is being sent to the server and before we have a confirmation
of content removal.
Change README intro
Eliminate some duplicate date-formatting code

Also remove arch-dependent compiler warnings for formatting strings with NSInteger.
Remove deprecated assignment to “isa” from bundled JSONKit

Use the recommended object_setClass instead.
Shut up “deprecated-objc-pointer-introspection” warning in bundled JSONKit
Small refactor in streaming client

Set maximum timeout to 50s (although polling will continue at normal 20s).
Merge pull request #27 from Livefyre/rc3

Rc3