Removed "distribute>=0.6.28" from pip_packages.txt because it was
breaking full builds of the ve (installation of the following package,
dye, was failing due to "ImportError: No module named setuptools").
Hamish initially added it because an older version of distribute on
someone's machine (maybe Ubuntu 10.04 or a CentOS server ?) would not
install some packages (mysql he thinks) without the newer version of
distribute. He did some testing (on Ubuntu 12.04, 10.04 and CentOS 5 and
6) and all installed fine without this line, so he was unable to
replicate the case where distribute version was too old. Lets revisit
this case if/when necessary.