Test for mocha-given doesn't run

I tried cloning the ```mocha-given``` repo and run the tests but it didn't work for me. I get this error:
```
/usr/local/lib/node_modules/mocha/lib/mocha.js:139
  if (!this._ui) throw new Error('invalid interface "' + name + '"');
                       ^
Error: invalid interface "mocha-given"
    at Mocha.ui (/usr/local/lib/node_modules/mocha/lib/mocha.js:139:24)
    at Object.<anonymous> (/usr/local/lib/node_modules/mocha/bin/_mocha:188:7)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:906:3
```

Here is a fix for it. I have create a test runner acording to the instructions in the readme file for ```mocha-given```. I changed the ```npm test``` command to use the test runner. I also added ```mocha``` as a local dependency since this will make the tests independent of global installs on the machine that runs them.