Fixes some minor issues related to karma 

1st commit fixes outdated karma dependencies which crash the `npm install` routine with the following error message:

``` 
npm ERR! peerinvalid The package karma does not satisfy its siblings' peerDependencies requirements!
npm ERR! peerinvalid Peer grunt-karma@0.6.2 wants karma@~0.10.0
npm ERR! peerinvalid Peer karma-mocha@0.1.3 wants karma@>=0.9
```

2nd commit adds `karma-chrome-launcher` to the devDependencies because it is set as the default browser in `karma.conf.js`

3rd commit updates the file location of chai.js

4th commit introduces the `singleRun` option within the grunt-karma config section to close the test browser after all tests have been executed. Otherwise grunt is not able to run any succeeding tasks.