Added test framework.

Can a proxy be running on the same system while we are running npm test?
(Well, it could, but will it happen?)

The problem is that the only way to specify the port that we have is through this same config file, so it's hard to launch a different Gonzales instance on another port for testing purposes.
I didn't find any way to specify a different config file with the 'config' module.

If this is important we could add a command line option.