Add a test

[ebengt]

This test only works for eunit test run as test, ie "rebar3 eunit".
It must be a git branch, ie in a git repo.

It only test compile.

Closes #14

[carlosedp]

This is great, thanks Bengt!
Maybe in the future we can improve it to check if the generated hrl and erl files have the correct content (or at least part of it).