Full rewrite

Instead of returning one cache setting, `redisify()` now returns a dictionary of all Redis URLs found in the environment settings, falling back on the default argument's value if one is provided. From the docstring:

    This method will look for Redis URLs in the environment settings. It
    will first check for ``REDIS_URL``. If this setting is found, it
    will be in the result ``dict`` as the ``default`` key. The method
    will then iterate through the settings looking for any additional
    Redis URLs. Any that are found will be added to the result ``dict``.

    In the event that ``REDIS_URL`` was not found, the first Redis URL
    encountered will be used as the ``default`` key. This URL will
    appear twice.

    In the event that ``REDIS_URL`` was not found and no other Redis
    URLs were found, the value provided through the ``default`` argument
    will be used as the ``default`` key.

    If ``default`` was no provided and no other Redis URLs were found,
    the ``dict`` will be empty.

This change results in a more useful tool with much leaner tests.
Fix typo in travis file

Oops!! This is one nasty typo. The test requirements are in the `tests` folder, not the `rests` folder. I think I must have called it rest because I should go to bed.
Make classifiers a list

PyPi doesn't seem to like when you use tuples