Don't do stuff you don't have to do
Avoid undefined index error.
Whitespace
Add action for additional custom instructions for shortcode
Add proper action for instructions
Optimize queries.
Bump minimum to 3.4, primarily because we're using wpdb::delete(). But also, why accommodate people who won't keep WP secure.  Silliness.
Merge pull request #7 from JustinSainton/master

Some general optimizations.