Wontinue when an initial handshake is successfull.

This seems to solve some blocking.
Although there seem to be some more problems.

See: telehash/gogotelehash#36
Merge pull request #25 from fd/cantinue-when-establishing-an-exchange

Continue when an initial handshake is successful.
Merge pull request #9 from telehash/master

resync with telehash:master