Remove Libav from TravisCI's list of required builds.
Remove Libav from TravisCI's list of required builds.

pupil-labs/PyAV,pupil-labs/PyAV,pupil-labs/PyAV,pupil-labs/PyAV,PyAV-Org/PyAV,PyAV-Org/PyAV,mikeboers/PyAV,mikeboers/PyAV