Escape test to be broken 

- `v0.3.0` of [expect.js](https://github.com/LearnBoost/expect.js)  renames main script file: from `expect.js` to `index.js`. In env where `expect.js@0.3.0` is installed, to run  `testem` will get error like below:


```
convert num array 
    ✘ expect is not defined
        ReferenceError: expect is not defined
            at Context.<anonymous> (http://localhost:7357/test/num_converter_test.js:10:3)
            at callFn (http://localhost:7357/testem/mocha.js:4338:21)
            at Test.Runnable.run (http://localhost:7357/testem/mocha.js:4331:7)
            at Runner.runTest (http://localhost:7357/testem/mocha.js:4728:10)
            at http://localhost:7357/testem/mocha.js:4806:12
            at next (http://localhost:7357/testem/mocha.js:4653:14)
            at http://localhost:7357/testem/mocha.js:4663:7
            at next (http://localhost:7357/testem/mocha.js:4601:23)
            at http://localhost:7357/testem/mocha.js:4630:5
            at timeslice (http://localhost:7357/testem/mocha.js:5761:27)
```

To fix this problem with minimum effort, I update `package.json` to specify  expect.js `v0.2.0`