Add test for commit message text-width check

Now that we have the testing infrastructure in place, add tests to give
more examples of testing hook checks.

Change-Id: I700f02484006c7fb621a6ace3fac8abfb19f3e14
Reviewed-on: https://gerrit.causes.com/23454
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>
Reviewed-by: Greg Hurrell <greg@causes.com>