set up travis (bug 1050156)

The test fix is to properly isolate it. In jenkins and locally, the tests running in their current order made it that the `tmp/packager` folder was created before this test ran.

The current [travis builds](https://travis-ci.org/magopian/olympia/builds) "only" have two failures (to be investigated, @davidbgk do you have a clue? FYI the https://travis-ci.org/magopian/olympia/builds/31926210 build has additional output), which is good enough as a starting point I believe ;)
eh, it should be "RUN_IN_CI" or something like that... but tbh, we should be able to drop that entirely... one day maybe. In the meantime, I'm trying to not modify anything that is not related to travis ;)