Add support for using requests

  - Enable the use of keep-alive (managed by sessions) to streamline a
    large number of API requests into a single HTTP connection for much
    improved performance.
Readme text to recommend use of requests.
Removing duplicate tests

  - We already tested those in the vanilla (urllib2) API tests.
Correcting terrible branch isolation practices

  - Roll back the tests that got introduced along with the cached
    timestamp branch.
Ensure tests for the requests library are done.
Merge branch 'master' into requests
Merge pull request #129 from metatoaster/requests

Add support for using the `requests` library.