Implemented to write test result summary to a txt file.

This looks to work fine. For stylistic and educational improvement, I suggest the following:

1. Write the log file before printing out all the results and declaring that we're done; and
2. Do that by wrapping  up the call to `fse.writeFile` in a promise. 

The latter will be tricky if you haven't practiced with promises much yet. Here is a very similar example of what I mean by "wrapping up the call in a promise":

https://github.com/adobe-photoshop/generator-assets/blob/master/lib/filemanager.js#L171

The flow of things here should be:
```
getTests()
  .then(/* reduce the tests into results*/)
  .then(/* write the log file */)
  .done(/* print ALL DONE */);
```
Here are the docs for Q, which is the promise library used by Generator: 
https://github.com/kriskowal/q
https://github.com/kriskowal/q/wiki/API-Reference

See in particular the function `Q.ninvoke` to wrap an asynchronous method invocation (like `fse.writeFile`) with a promise:
https://github.com/kriskowal/q/wiki/API-Reference#qninvokeobject-methodname-args