Adding new `all=True` param to our `groups_required` decorator.

This will allow users to specify whether or not they want to force users to be a
member of every group, or just one.
Adding tests to assert that the new `all` param works.
Modifying our groups_required decorator.

It now handles:

- Objects.
- hrefs
- names
- An all param, which lets you assert whether a user is in one group, or many.
Adding groups_required api docs.
Updating our docstring example of groups_required.

For clarity!
Adding a 'How Do I ... ?' doc section.

This covers how to assert group membership easily.
Updating changelog with release info.
Verison bump.
Merge branch 'release/0.1.0' into develop

* release/0.1.0:
  Verison bump.
  Updating changelog with release info.
Merge pull request #3 from rdegges/develop

Release 0.1.0.