Merge pull request #27 from danielballan/sphinx

DOC: Remove mr docs, update trackpy docs.
Merge pull request #28 from danielballan/sphinx

Sphinx
Merge pull request #29 from danielballan/sphinx

BLD: Fix dependency links.
Merge pull request #30 from danielballan/sphinx

DOC: Add link to ReadTheDocs.
DOC: More ReadTheDocs tweaks.