Fixed Issue #217 - memory leak caused by Thread(this).


- `writeThread = new Thread( this );` caused a circular reference so WebSocketClient and writeThread was never garbage collected.
- use 2 thread instance variables instead of starting `writeThread` with a `read`, then reassigning it as a writer in it's run method. Now there is a `readThread` and `writeThread`, as WeakReference<Thread>

#### Before Fix - 242 Objects Retained ####
![screen shot 2013-11-21 at 9 48 31 am](https://f.cloud.github.com/assets/1975119/1592957/6e0511de-52c4-11e3-9abc-0d392edd6587.png)

#### After Fix - 1 Object Retained####
![screen shot 2013-11-21 at 9 50 46 am](https://f.cloud.github.com/assets/1975119/1592971/b16ffd44-52c4-11e3-979a-87fc904cf547.png)