conda update: don't try to update packages that are already up-to-date

This should hopefully fix #463, because now `conda update anaconda` will do
nothing if anaconda is already at the latest version.  If the package is not
the latest, it will work just as it did before. If you want the old behavior,
use `conda install` instead of `conda update`.
Travis: install conda last, so it doesn't get downgraded
Merge branch 'master' into all-solutions