add license file

This node module's package.json indicates that it is licensed under the MIT license.

The thingy most people call the MIT license states:
```
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
```

In order to comply with the terms we believe you wish your code to be used under, we are including the copy of the LICENSE file included with this pull request with the Fedora package for this module.

If our assumption is incorrect, please let us know. If you'd like to make it easier for others to reuse your work in the future, please merge this pull request.

Thanks!