[travis] Remove system_site_packages
[travis] Remove system_site_packages

System site packages only works for Python 2.7 and 3.2, so remove for
3.3 and 3.4. Also install liblapack because it seems like cvxopt does
not find atlas.

yasserglez/pymdptoolbox,sawcordwell/pymdptoolbox,silgon/pymdptoolbox,McCabeJM/pymdptoolbox,McCabeJM/pymdptoolbox,silgon/pymdptoolbox,sawcordwell/pymdptoolbox,yasserglez/pymdptoolbox