Add API docs.

Sources are generated by "make apidocs". The modules.txt file is
pulled into index.txt.
Merge branch 'master' of git://github.com/sgillies/shapely into py3
Add .travis.yml to start testing with Python 2.6, 2.7, 3.2 and 3.3
Move Python 3 decode to just 'errcheck_just_free'