Packaging for gom - a Go dependency manager

https://github.com/mattn/gom

Package is named golang-gom because there's an existing unrelated package called gom in Ubuntu.
there are no tags or anything in the upstream repo, so I locally tagged the first commit in the repo as '0', then used git describe to generate that version.  the 122 is a count of the commits between the tag and HEAD, necessary to ensure the version number will always increase for later commits.

Having written this, it feels as though this should be captured somewhere, but I'm not sure where...