Switched to a data attribute for the toggle selector (separates scripts from styles).

Also…
  * Removed unneeded `.save-form-data` and `.delete-form-data` classes.
  * Replace `.hide-no-js` with `.form-saver` wrapper class.
  * Updated code structure for better modularity.
  * Prefixed script with a `;` to prevent errors if other scripts are
incorrectly closed.
  * Added namespacing to IIFE.
A few minor fixes