Various Improvements

Added link to demos on all appropriate pages and added a list of all demos (`/demo/index.html`), added link and select option value to demos (`/index.html`), consolidated var usage and added custom, complete mobile detection (`/lib/codemirror.js`), created `index.php_` to generate HTML for demo list (obviously rename it with a `.php` extension to view), and added a minified copy of the current JavaScript library's development version.