Updated javascript

[According to MDN](https://developer.mozilla.org/en-US/docs/JavaScript/Guide/Functions#escape_and_unescape_functions%28Obsoleted_above_JavaScript_1.5%29), the escape/unescape functions in javascript are deprecated and instead encodeURIComponent/decodeURIComponent should be used.

I discovered this while I had some trouble with pluses being interpreted as spaces when using the Tester.

This patch replaces the javascript functions in use and fixes the issue.