improve docs for fuzzywuzzy.process

The documentation for this module was dated and sometimes inaccurate.

This overhauls the docs to accurately describe the current module,
including detailing optional arguments that were not previously
explained - e.g., the `limit` argument to `extract()`.

This change follows the [Google Python Style Guide](https://google-styleguide.googlecode.com/svn/trunk/pyguide.html?showone=Comments#Comments) for comments.