v0.57n 2010-03-24 - added support for last modified and expires headers. these
will be better used with a persistent cache.
v0.56n 2010-03-24 - added support for generic urllib2 url openers, with https
as included example
v0.55n 2010-03-24 - moved all imports out of the get_file mechanism, to avoid
recursive urlimport attempts.
v0.54n 2010-03-23 - remove file from cache when this is disabled.
v0.53n 2010-03-15 - split perforce class from other urls
v0.52n 2010-03-14 - allow cache disabling for certain urls and hosts
v0.51n 2010-03-13 - allow setting ssl keys/certs for specific urls and hosts
v0.50n 2010-03-12 - fixed bugs with cache building when submodules present
v0.49m 2010-03-10 - pyo, pyc support, mac source newlines, fixed minor bugs
v0.48m 2010-02-26 - pydXX support
v0.47m 2010-02-04 - reset function added
v0.46m 2010-02-03 - perforce bug fix
v0.45m 2010-02-03 - pyd bug fix
v0.44m 2010-01-31 - perforce support
v0.43m 2010-01-25 - pyd support
v0.42m 2010-01-22 - added cache function & hid some logs