specify a minimum pytz version

[fungi]

Babel 1.0 depends on pytz without specifying a minimum version. Pytz uses date-based versioning with letters. Pip 1.4 sees all version strings containing letters as prereleases and will not install them without being asked to do so. The upshot of this is that installing latest Babel with latest pip fails unless any version of pytz is manually installed first.

One common way to work around this issue is to have the pytz dependency specified with a minimum version which contains a letter, for example "pytz>=0a".

[fungi]

Information on the behavior change in pip 1.4 can be found at pypa/pip#974 .

[mitsuhiko]

Done now and 1.1 is out.