Log Message:
Update py-betamax to 0.6.0.

0.6.0 - 2016-04-12
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- Add ``betamax_recorder`` pytest fixture

- Change default behaviour to allow duplicate interactions to be recorded in
  single cassette

- Add ``allow_playback_repeats`` to allow an interaction to be used more than
  once from a single cassette

- Always return a new ``Response`` object from an Interaction to allow for a
  streaming response to be usable multiple times

- Remove CI support for Pythons 2.6 and 3.2