WIP global: travis fixes

* Adds the language key (otherwise, [it's ruby](http://docs.travis-ci.com/user/getting-started/#Step-three%3A-Add-.travis.yml-file-to-your-repository)).
* Downloads the devscripts where they want to be downloaded.
* Moves `apt-get update` to `before_install` as [advised](http://docs.travis-ci.com/user/build-configuration/#Build-Lifecycle)
* Enables the Python 2.6 build, even if it doesn't look like it.

**blockers:**
- [ ] tiborsimko/invenio-devscripts#17
- [ ] bibknowledge requires libxml2 (#1879)
See https://code.google.com/p/modwsgi/wiki/ConfigurationDirectives#WSGIDaemonProcess