Add test for lua

I added a test for the lua chcker. It needs lua-mode package from elpa. However I dont use the  melpa package by myself, because it doesn't work. It crashes my emacs on opening a lua file and there is an output from lua-mode in the minibuffer `prefix key set to "C-c"`. I use the lua-mode package from my debian/ubuntu package manager.
The test however works with the melpa version of lua-mode, but there is this output "prefix key set to C-c".
I could have added `sudo apt-get install -yy lua-mode` to the vagrant script but I dont't know how you want to handle the install of lua-mode generally for the tests.