Allow better usage of docs locally.

[sontek]

This will default to the rtd theme and introduces
tox -e docs for generating docs locally.

[sontek]

Tests are failing because we haven't merged in:

#314

For the pypy fix.

[coveralls]

Coverage remained the same at 89.27% when pulling c88e3ce on sontek:add_docs_to_tox into 3ab9a42 on mumrah:master.

[coveralls]

Coverage remained the same at 89.27% when pulling c88e3ce on sontek:add_docs_to_tox into 3ab9a42 on mumrah:master.

[coveralls]

Coverage remained the same at 89.27% when pulling c88e3ce on sontek:add_docs_to_tox into 3ab9a42 on mumrah:master.

[sontek]

You can see how this looks here:

http://sontekkafka-python.readthedocs.org/en/add_docs_to_tox/apidoc/modules.html

[sontek]

This also fixes: #318

http://sontekkafka-python.readthedocs.org/en/add_docs_to_tox/apidoc/kafka.html#module-kafka.client