Log Message:
Updated py-betamax to 0.8.0.

0.8.0 - 2016-08-16
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- Add ``betamax_parametrized_recorder`` and ``betamax_parametrized_session``
  to our list of pytest fixtures so that users will have parametrized cassette
  names when writing parametrized tests with our fixtures. (I wonder if I can
  mention parametrization a bunch more times so I can say parametrize a lot in
  this bullet note.)
- Add ``ValidationError`` and a set of subclasses for each possible validation
  error.
- Raise ``InvalidOption`` on unknown cassette options rather than silently
  ignoring extra options.
- Raise a subclass of ``ValidationError`` when a particular cassette option is
  invalid, rather than silently ignoring the validation failure.