Merge branch 'bc/git-p4-for-python-2.4'

With small updates to remove dependency on newer features of
Python, keep git-p4 usable with older Python.

* bc/git-p4-for-python-2.4:
INSTALL: git-p4 does not support Python 3
git-p4.py: support Python 2.4
git-p4.py: support Python 2.5