Changes to code editor behavior

Hey, I changed the behavior of your code editor a bit. Here are the things I've changed:
 - Stop if the user modifies the code while running
 - Remove any formatting from the code editor as the user types (useful when somebody pastes from pages with custom formatting)
 - Don't wrap code in the editor: you can now scroll horizontally if your lines are long
 - Allow vertical resizing of the editor to make it easier to deal with longer programs
 - Clearfix on the actions bar
 - `display: block` on the editor div
 - Editor div is a bit taller and with a slightly increased `line-height`

Hope you like it!