Update py-flask-script to 0.6.0.

Version 0.6.0
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Released on August 7, 2013.

- Drop support for Python 2.5
- Support Python 2.6/2.7 and >= 3.3 using same source code.
  Import necessary compatibility code from flask._compat module of current
  Flask repo code.
- Use proper argparse subparsers
- Tab completion using `argcomplete`
- Remove question marks from automatically being appended to
  prompt_bool and prompt_choices
- FIXED: ipython with disabled bpython
- FIXED: debug parameter no longer passed in from flask_script
Updated www/py-flask-script to 0.6.0.