Initial work on threading.

Rough around the edges but fixes:
* Connection leak
* Inability to connect to remote hosts
Look for cberl_drv.so not cberl_nif.so.
Implemented cleanup routines.
Updated copyrights, authors etc.

Added changelog.
Fixed thread init/teardown bug which caused segfault on badarg.

Fixed mem leaks in args handling on badarg condition.
Fixed CAS bug. CAS value now is now unsigned.
Merge pull request #7 from wcummings/master

Now uses threads