update travis config

use UNIT_TEST=1 so as not to have to worry about installed modules breaking the
tests of other modules
[WIP] test an experimental maintainer-quality-tools branch
experimental branch merged
keep an env with most modules installed

@pedrobaeza and @dreipt argued this was a good idea
Merge pull request #16 from gurneyalex/8.0-update-travis

update travis config