Add explicit positional argument specifiers to .format() strings

Add explicit positional argument specifiers to .format() strings

This fixes issues with Python 2.6 (before the implicit specifiers
introduced by Python 2.7).

  On Fri, Nov 16, 2012 at 09:04:56AM -0600, Daniel Heater wrote:
  > ...
  > Traceback (most recent call last):
  >   File "setup.py", line 22, in <module>
  >     version='{}'.format(version.version()),
  > ValueError: zero length field name in format
  > ...