awful.tag order regression fix based on discussion on https://awesome.naquadah.org/bugs/index.php?do=details&task_id=1249
Revert "revert 9c69e8: do not set index to nil after setscreen---this breaks awful.tag.move etc."

This reverts commit 1ca6eabe31e57c0de9a9c57a89ebc77a865e79ea.
add build script for Arch Linux host