HTTPie 0.9.0

• Added --cert and --cert-key parameters to specify a client side
  certificate and private key for SSL
• Improved unicode support.
• Improved terminal color depth detection via curses.
• To make it easier to deal with Windows paths in request items, \
  now only escapes special characters (the ones that are used as key-value
  separators by HTTPie).
• Switched from unittest to pytest.
• Added Python wheel suppor.
• Various test suite improvements.
• Added CONTRIBUTING_.
• Fixed User-Agent overwriting when used within a session.
• Fixed handling of empty passwords in URL credentials.
• Fixed multiple file uploads with the same form field name.
• Fixed --output=/dev/null on Linux.
• Miscellaneous bugfixes.