Add CI - preferrably Travis-like, but it must support VirtualBox

[gunnarx]

Help wanted: A public, free-for-open-source CI service that supports Vagrant & VirtualBox from the build instructions.

• Travis-CI does not support it.
• Semaphore has an article about using Vagrant, but it does not speak at all about using Vagrant in a Semaphore build, so IDK if it supports it.
• For GENIVI Go.CD server we have a special agent that runs virtualbox builds, but I'm looking for something simple and directly integrated with GitHub like Travis-CI