[LinuxCNC/linuxcnc PR#137] build: include metadata for Travis CI integration

Travis CI is not the equal of buildbot (it can’t run RT kernels and can only test building on Ubuntu with amd64) but adopting it in addition to buildbot would let us do things like automatically build-test pull requests on github without developer interference (i.e., by pushing a temporary branch to glo)

In addition to these commits, additional behind the scenes configuration of the (free as in beer) travis-ci.org webservice is required.

I’ve mildly tested this (it took just an hour or so to get it working) using my fork of linuxcnc. You can see the result of a travis build of linuxcnc here: https://travis-ci.org/jepler/linuxcnc