Bug 1241144 - Travis: Update pip from v7.1.2 to v8.0.0
Bug 1241144 - Travis: Update pip from v7.1.2 to v8.0.0

So that we can confirm that peep still operates under pip v8, prior to
the transition from peep to pip v8's new hashing feature.

https://pip.readthedocs.org/en/stable/news/

glenn124f/treeherder,tojonmz/treeherder,wlach/treeherder,glenn124f/treeherder,akhileshpillai/treeherder,tojonmz/treeherder,edmorley/treeherder,glenn124f/treeherder,KWierso/treeherder,tojonmz/treeherder,tojonmz/treeherder,kapy2010/treeherder,wlach/treeherder,wlach/treeherder,kapy2010/treeherder,kapy2010/treeherder,tojon/treeherder,glenn124f/treeherder,akhileshpillai/treeherder,wlach/treeherder,edmorley/treeherder,glenn124f/treeherder,akhileshpillai/treeherder,wlach/treeherder,akhileshpillai/treeherder,wlach/treeherder,tojon/treeherder,edmorley/treeherder,kapy2010/treeherder,tojon/treeherder,tojon/treeherder,tojonmz/treeherder,KWierso/treeherder,glenn124f/treeherder,akhileshpillai/treeherder,edmorley/treeherder,kapy2010/treeherder,KWierso/treeherder,tojonmz/treeherder,KWierso/treeherder,akhileshpillai/treeherder