Added 'npm test' to run unit tests and Wercker to automate the testing

Hello,

Added to package.json file 'scripts' object, so that you can run your unit test with 'npm test'.

Added also Wercker, which is similar to Travis CI, to the project for automating the test and build process.  A wercker.yml file can be found in the root of your project. The ReadMe.md file has a Wercker badge to notify you about the build status. 

You can take Wercker into use by following these steps: 

1) Register to Wercker: https://app.wercker.com/users/new

2) After loggin in to Wercker, add your app from the left navigation pane to the service. 

3) Pushing changes to the repo will trigger a new build on Wercker. 

Kind regards,

Oona