Add support for spawing with Tyrannical arguments (Finally!!!)

It is now possible to spawn with an array of properties, see the README.md
for more details. It require Awesome 3.5.3+, some patch will get into 3.5.6
to make this even better. I also added the 'new_tag' property to be used
with spawn.

* Also fix issue #37, sorry about that one...