misc: added script to test git-hooks

Recently, we had some failures in those hooks. The script is hacky, but
it's googd enought to host it on our continuous integration environment
(I will rewrite it later, don't worry).  The next step is redeploy
pre-receive and post-receive hooks whenever they change (automatically).
Makefile: run git-hooks tests on test target

Let's see if drone and travis like this script :)