DOC: fixed additional small typo in installation docs#125

Merged

slivingston merged 3 commits intopython-control:masterfrom

murrayrm:doc-update

Jan 1, 2017

Commits on Dec 29, 2016

DOC: fixed small typo in installation docs + add prereqs
murrayrm
committed

Commits on Dec 31, 2016

TRV: removed trailing spaces
murrayrm
committed

Commits on Jan 1, 2017

TRV: fixed grammatical error in conda instructions
murrayrm
committed