Do not mask websocket frames on send.

This fixes websockets for Chrome. Without this fix a connection attempt to a
libonion websocket server is immediately terminated with the following error message:
WebSocket connection to '[...]' failed: A server must not mask any frames that it sends to the client.
Merge pull request #48 from dschwen/master

Do not mask websocket frames on send.

My fault, as I see now, server should not mask responses; section 10.4 af RFC 6455:

As such, it was not deemed necessary to  mask data in both directions (the data from the server to the client  is not masked).

Thanks!