Fixes bug with duplicate headers on user group lists.

Returns an array of `WP_User` objects based on the taxonomy & term.

Fixes #5.

This is a bit of a hack, that assumes there is no user with the ID of `0`. There shouldn't be, but who knows what some plugins might be doing. Maybe `PHP_INT_MAX` is a better idea, but we'll reserve that for later.

Fixes a bug that would default to showing all users if there were no users in a group.

Add a unique class to each tax-form.

Link correction in README.md

Make all strings translatable

Fixed link to support forum