maint: pass LUA to all make invocations for Travis CI.
maint: pass LUA to all make invocations for Travis CI.

* .travis.yml (script): Pass LUA to all make invocations.

Signed-off-by: Gary V. Vaughan <f9023000f29773649f3850298becb9544b5fd6a9@gnu.org>

gvvaughan/specl