New attack on #88. Added buffering.
Composed process termination differently.

Now there is way to terminate process wrapper when data already passed
to backlog buffer.

Removed extra "close" calls and not-needed demuxing
"subscribe/unsubscribe" feature.
Removed test that's not implemented yet,...

 added interface to decouple from websocket lib in future tests.
Merge pull request #90 from asergeyev/master

Follow up on #88, introducing ways to handle big messages and slow network.