Start global state reorg.
Steps on globalstate.
Merge remote-tracking branch 'upstream/master' into global_movers

Conflicts:
	opentis/calculation.py
added engine_store.py
cleanup
cleanup
fixes and corrections for testopenmmengine
Mostly comment updates; a little restructuring
Zeroth order version of SampleSet

Untested, probably full of problems. But I hope this is enough that JHP can
add storage support.
Finished draft of SampleSet.

Now I need to start writing tests for it to make sure it does what I think
it does.
Skeleton of tests for SampleSet.
Test PR. Having issues with running tests locally

Could be a problem with my local install; want to see if Travis will pass
this. This is the current choderalab/master, plus an empty file, so if it
doesn't pass the tests then the question becomes version numbers and such.
Maybe this gives us msmbuilder.metrics?
Removing empty tmp file
Fixes based on first group of tests.
Fixes to SampleSet.__delitem__ and more tests.
SampleSet: more tests, better docs.
SampleSet: added SampleKeyError. And more tests.
Merge remote-tracking branch 'dwhswenson/sample' into samplestorage
moving classes