Removes unnecessary imports
Updates pyon submodules

Previous HEAD position was 21b071f... Merge pull request #395 from lukecampbell/time_profile
HEAD is now at a2dfe2c... Merge pull request #396 from lukecampbell/time_profile-r2
Merge pull request #120 from ooici/submodules-r2

OOIION-1310 Updates submodules in Coverage Model