Adding 'unsubscribed_from_emails' to the Users object.
Fixing User.all() to return all users, not just the first page
Parameters added to the get_users method: page, per_page, tag_id, and tag_name.
Message thread now has 8 properties in it's reponse object.
Add the get_users parameters to `User.all`.
Adding support for per_page, page, tag_id, and tag_name.
Also adding unsubscribed_from_emails attribute to User.

Thanks https://github.com/sdorazio
Merged pull request from @sdorazio which fixes the ``User.all``
method to return all users and adds ``unsubscribed_from_emails``
attribute to ``User``.

Removed change to ``User.all`` that added named parameters.
Exit with 1 if any doctests fail.
Adding support for `last_request_at` to `User`, `create_user`, and `update_user`.

Fixes #16
Changelog and version number bump.