Refactor the surrogate keys we've used
Refactor AttributeDict

* Moves AttributeDict into warehouse.datastructures
* Refactors convert_to_attr_dict to just be the __init__ for
  AttributeDict
Declare constants for the Fastly surrogate keys
Merge pull request #265 from dstufft/refactor-fastly-cache

Use a Standard Set of Fastly Surrogate Keys
Updated setup.py to indicate that it runs on Python 3.4+
Merge pull request #271 from agronholm/master

Updated setup.py to indicate that it runs on Python 3.4+
Allow whitelisting the CDN for trusting the X-Forwarded-* headers
Merge pull request #272 from dstufft/x-forwarded

Allow whitelisting the CDN for trusting the X-Forwarded-* headers
Add py.test to the dev requirements
Ensure prev/next properties behave with 0 results
Hide prev/next links if they're not present

Rather than only making a link if they're present, simply hide them
entirely if they aren't.
Replaced the uses of "mock" with the standard library's unittest.mock
Added Alex Grönholm to AUTHORS
Merge pull request #274 from necaris/no-prev-next-with-no-results

Don't show prev / next elements when they're not available
Merge pull request #275 from necaris/pytest-in-requirements

Add py.test to the `dev-requirements.txt`
Merge pull request #277 from agronholm/mock

Mock