This directory holds files that are only needed for the 'local'
version of khan-exercises -- e.g. sandcastle.kasandbox.org.

These files are needed to view the exercises, but in production -- at
www.khanacademy.org -- are provided by the main khan academy website.
For instance, if you're viewing an exercise at
   https://www.khanacademy.org/math/arithmetic/addition-subtraction/basic_addition/e/number_line
then that page has loaded jquery.js from
webapp/javascript/shared-package/jquery.js.  (It needs jquery to
display the chrome/etc around the exercise.)  We don't need an
exercise-specific version of jquery.js as well.  However, if you're
viewing the same exercise at http://sandcastle.kasandbox.org/
there's no chrome loading jquery.js, so the exercise has to do it
itself.

The script
   update_local.sh
will update this directory from the webapp repository.

If you add a file here, also add it to
   ./update_local.sh
   ../khan-exercise.js:initScripts
