Added conditional logic for handling earlier versions of Python.

o For Python versions < 2.6, I've added a string formatter that works
  like str.format(). Running pygrep with Python versions >= 2.6 uses the
  standard str.format().

o For Python version < 2.5, I've added appended OptionParser()'s epilog
  string to the description. Runnin pygrep with Python versions >= 2.5
  passes OptionParser() the epilog argument directly.
Added error handling for str.format() when {} is used for a field spec.

o It turns out that, at least in Python 2.6, str.format() doesn't
  actually support {} as a field specifier. (That comes along with
  Python 2.7.) So I'm using my own format function for Python
  versions < 2.7 now.

o I've also re-added the -1 command line option. It was lost because
  I've been doing development on an old machine where git isn't
  installed, and I rsync'd over the source for that feature.