Merge pull request #36 from openworm/neuromlpopulation

Neuromlpopulation
remove unnecessary comments
Merge remote-tracking branch 'origin/neuromlpopulation' into development
Release 0.1.7
Track when trees are emptied
expands modified flag to entity and aspect nodes. Changes to serializer
to take in consideration modified flags for entity and aspect. Cleans
serializer code, adds more junit tests to perform network tests, and
further tests on existing serialization of trees.
Merge branch 'development' into neuromlpopulation