Remove highlighting of numbers for consistency with other major-modes

See http://lists.gnu.org/archive/html/emacs-devel/2011-06/msg00565.html
for a history of analogous discussion concerning python-mode.
Add basic indentation tests
Add missing modulo operator (%) to line-continuation tokens
Remove syntax hacks for '.' & '_' characters
Rewrite lua-send-buffer function (should fix issue #60)