Don't install RBTools on Python < 2.5

Review Request #5212 — Created Jan. 7, 2014 and submitted — Latest diff uploaded

Information

RBTools
master

Reviewers

Don't install RBTools on Python < 2.5

This adds a check to setup.py to enforce a minimum python version, like the one
we have for Review Board.

Tried installing on a system with 2.4.x and saw the error.