* Merge _crs into crs
CRS is an extension class now, with improved documentation. The
test__crs.py file is obsolete and has been deleted.
I piggy-backed some API doc changes onto this. We now generate
API docs from scratch every time and have removed the .rst files
from the repo. The crs module now uses the embedsignature Cython
directive, which we should do for other extension modules.
* Include private modules
* Restore API docs
We'll remove them in a different branch.
* Update docs/index.rst
* Handle OverflowError from <int>code
Also repair chunks missed in rebase
