add licenses directory

Includes scipy and sphinx-bootstrap-theme licenses. Necessary because I copied a couple of files from their sphinx documentation areas.
Add sphinx doc area

Uses layout similar to numpy, scipy, and pandas, where each function, class, method, attribute, etc. has its own page.

Uses sphinx-bootstrap-theme and numpydoc. Currently only links to bipy.core.distance documentation.
update travis to test doc building

Tests building of docs (no errors or warnings) and links.
fix sphinx-bootstrap-theme name
conda doesn't have sphinx-bootstrap-theme

moved to an explicit pip install command
update numpydoc version in travis conf file
add strict checking in sphinx makefile
Merge branch 'master' into issue-86
address comments from @gregcaporaso

Also fix a couple of sphinx errors in the sequence docstrings
complement_map is now a static member

Also removed strange scoping/binding issue with temporary 'c' variable used to build the alphabet static variable.
Merge pull request #122 from jrrideout/issue-86

bipy sphinx docs