- Fixing concurrent race that occurs when calling delegate with
websocketDidReceiveMessage and websocketDidReceiveData with a default
priority queue which so happens to have higher 1 concurrency level.
Also this ensures delegate is always fired on the main queue making
the library easier to use.
- Declare delegate as weak to avoid strongly holding onto the delegate.
Merge pull request #18 from robskillington/fix-interleaved-delegate-callbacks

Avoid default priority queue which can be concurrent causing out of order messages delivered to delegate