Fix for Issue #9

- ARC is more aggressive than retain/release/autorelease used to be, and it is causing occasional issues on disconnect
- It appears that TCPConnection's "sAllConnections" static mutable array variable is never (and has never actually been) initialized to an real NSMutableArray object.
- Added initialization for that array, seemed to fix the issue in most, but not all cases.
- Flipping the strong/weak property/ivar references between TCPStream and its TCPConnection object, combined with the sAllConnections array appears to have solved the issue entirely without introducing any leaks that I can see.