travis: initial config

Reasons for using 'make -j2':
1) Test parallel build
2) Faster
3) <henrikhodne> Nikoli: I don't think we allow/don't allow a certain -j value, but the VMs each have 1.5 cores allotted to them.

http://about.travis-ci.org/docs/user/notifications/
"
Travis CI can notify you about your build results through email, IRC and/or webhooks.

By default it will send emails to
    the commit author and committer
    the owner of the repository (for normal repositories)

And it will by default send emails when, on the given branch:
    a build was just broken or still is broken
    a previously broken build was just fixed
"