This removes matplotlib as a dependency by default.  Along with it, clear out some un-used code
Deleted integration test which relied on ImageSensor
Restoring ImageSensor.py and network serialization integration test
Except all when importing
Slightly more graceful approach to initializing pylab if it's available.
Merge remote-tracking branch 'upstream/master' into optional-matplotlib
Merge pull request #377 from oxtopus/optional-matplotlib

Matplotlib no longer required by default
Merge branch 'master' into reduced-mem-omit_store