Added hull.py (from dynamiq r199).
Corrected permissions on hull.py. (644, not 755)
Draft of hull_volume; minor additions to hull.

I'm keeping the original hull.py file separate so that I can easily sync it
between msm-tis and dynamiq. I've generated a separate hull_volume file for
the msm-tis Volume object version.
Oops; forgot to add hull_volume in previous commit.
Implemented potentially useful methods in hull.py.

* `hull_facets()`: returns vertex numbers to describe the facets on the
  hull.
* `vertex_list_to_points()`: return spatial points for a list of vertices
  (maintaining array shape)
Betters docs for hull and hull_volume.
Merge pull request #5 from dwhswenson/hull_volume_iss2

Adds hull and hull_volume.
Better docs on hull and hull_volume.
Merge branch 'master' of github.com:choderalab/msm-tis

Bringing JHP's updates to choderalab/master into my own master/
Merge remote-tracking branch 'upstream/master'

Should be the most workable version of JHP's storage and trajectory format;
enough to allow me to then bring this into my XYZ branch.
Merge pull request #15 from dwhswenson/master

Delaunay triangulation based "hull" and hull_volume