Make sure latest version of virtualenv is available on travis.
Make sure latest version of virtualenv is available on travis.

Plexxi/st2,Plexxi/st2,Plexxi/st2,StackStorm/st2,nzlosh/st2,StackStorm/st2,nzlosh/st2,Plexxi/st2,nzlosh/st2,StackStorm/st2,StackStorm/st2,nzlosh/st2