Bypassed threading in CommandDispatcher.put().  Makes a huge
improvement in performance for individual calls to Couchbase.

This was a very quick fix which needs to be implemented a bit
less hastily sometime soon.
Removed threading from CommandDispatcher in couchbaseclient.py
fixed so client actually receives streaming updates from
Couchbase server.

Also fixed memory leak.

Added "prefetch=False" to requests and "del(line)"
to the following methods
    - Client:_start_streaming()
    - CouchbaseClient:_start_streaming()