Tap.py

----------------------------------

* Add support for producing TAP version 13 output
to streaming and file reports
by including the ``TAP version 13`` line.

----------------------------------

* Add optional method to install tappy for YAML support
with ``pip install tap.py[yaml]``.
* Make tappy version 13 compliant by adding support for parsing YAML blocks.
* ``unittest.expectedFailure`` now uses a TODO directive to better align
with the specification.

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* Add support for Python 3.6.
* Drop support for Python 3.3 (it is end-of-life).
* Use Pipenv for managing development.
* Switch to pytest as the development test runner.

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* Add ``Parser.parse_text`` to parse TAP
provided as a string.

-----------------------------------

* Remove nose plugin.
The plugin moved to the ``nose-tap`` distribution.
* Remove pytest plugin.
The plugin moved to the ``pytest-tap`` distribution.
* Remove Pygments syntax highlighting plugin.
The plugin was merged upstream directly into the Pygments project
and is available without tappy.
* Drop support for Python 2.6.

------------------------------------

* ``TAPTestRunner`` has a ``set_header`` method
to enable or disable test case header ouput in the TAP stream.
* Add support for Python 3.5.
* Perform continuous integration testing on OS X.
* Drop support for Python 3.2.