Added CasperJS and Zombie.js to Testing

Functional testing tools for server-side JavaScript seem to be missing from the list. CasperJS is a useful tool that provides a testing framework on top of PhantomJS. Zombie.js is an alternative to PhantomJS (and can be used with regular assertion libraries in place of CasperJS).
Merge pull request #1 from asifrc/master

Added CasperJS and Zombie.js to Testing