Fix coloc docs

[aeisenbarth]

The colocalization was not included in documentation.

This was because we have Sphinx set up to document only explicitly (discovery with sphinx-apidoc often gives unwanted results). automodule has an option :imported-members: but it only includes directly imported functions, not modules.

So I added a separate, explicit section for the colocalization module.

Closes #19

[tdrose]

Looks good. Thanks for fixing typos.