Merge pull request #138 from vermiculus/editing-fix

Editing fix
Improve some header comments.
Bring sx.org up to date
Expand the Contributing section.
Create sx-load file whose sole purpose is to load everything.
Update sx.org
Merge pull request #139 from vermiculus/updating-sx.org

Updating sx.org
Merge pull request #140 from vermiculus/requires

Properly order our `require`s
Create sx-babel

Has functions and a variable for font-locking pre blocks.
Patch sx and sx-question-print to use sx-babel.
Don't require sx

Requiring sx is not needed because the macro is autoloaded.
Fix some implementation bugs
Update sx.org