Add support for Phantom 2

Phantom 2 removes the args property from the phantom object.  That property has been deprecated for awhile, and this PR stops using it.  Unit tests pass on OS X 10.9.5 with PhantomJS 1.9.7 and 2.0.0.

Details on the args property are here:
http://phantomjs.org/api/phantom/property/args.html

PhantomJS 2.0.0 snapshot binaries are available here:
https://github.com/bprodoehl/phantomjs/releases