Refactored capsule server and fixed bug

[cosmadrian]

This PR addresses issue #26.

Removed duplicate code for capsule_zmq and capsule_mpc, now both are operating from capsule_server. The capsule_server/local_server.py script now accepts two flags, one for the type of tasks that it handles (mpc or zmq) and the port. Capsule server now sends pickled dictionary responses that contain a 'success' flag. When success is false, an exception is thrown at the client side. On the capsule client, exception handling for the new 'protocol' is done in an unobtrusive way, by means of the TaskSocket class that wraps zmq.socket. Changed build_and_run.sh script to reflect these changes.