test with Python 3.4 on Travis

exclude redundant js tests on 3.3
Don't hang tests if notebook server fails to terminate.
Popen.wait(timeout) is new in Python 3.3
cleanup socket cleanup

- set linger on sockets (avoid hang on exit)
- actually close sockets, not just zmq streams (blame pyzmq, aka me)

seems to be necessary for js/notebook/shutdown test to avoid hanging on Python 3.4.
set linger on every socket I can find

help cleanup sockets on 3.4
reorder travis so slowest groups start first
Merge pull request #5759 from minrk/travis-3.4

test with Python 3.4 on Travis