Slumber

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* Added a ``session`` kwarg to ``slumber.API`` allowing passing a ``requests`` session
that will be used instead of the slumber created one

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* *(Backwards Incompatible)* Switched from ``httplib2`` to ``requests``
* *(Backwards Incompatible)* Removed the Meta class Magic
* *(Backwards Incompatible)* Removed the ability to subclass ``slumber.API`` to specify defaults
* *(Backwards Incompatible)* New Syntax for Specifying Authentication

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* Fix regression where pre 0.3 urls were assumed to end in slash, and 0.3.0 presumed to end in not slash.
Urls are now assumed to end in a slash, and if you don't want this behavior you can disable it by the
append_slash kwarg/Meta option (set to False to disable it).
* Fix regression caused by a mistyped variable name.

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* Allowed nesting resources infinitely to allow more complex api usage.
* Cleaned up the Meta class and allow subclassing ``slumber.API``
* *(Backwards Incompatible)* Cleaned up the exception names.
* *(Backwards Incompatible)* Renamed the ``slumber.API`` serialization kwarg from
default_format to format to be more consistent
* Improved the documentation
* Added Some Tests (This could still be better)

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* Fixed https urls and the accidental force to port 80
* Fixed the assumption that all urls end in a trailing slash

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* Fixed Including of Changelog.rst