RO 3.6.0

- This version requires Python 2.6 or 2.7. Earlier versions of Python are no longer supported.
- Removed RO.Future.subprocess and RO.Future. The subprocess module has been available for a long time.
- Many internal cleanups, based on work by Madison Stemm, including:
    - Changed StandardError to Exception and always raise exceptions with <i>Exception</i>(arguments)
    - Changed iterator.next() to next(iterator)
    - Use the print function instead of the print statement (using <code>from __future__ import print_function</code>)
    - Removed the #! line from modules and unset the "x" mode bit on modules that do not contain executable code
    - Defined __all__ in most modules