Fixes #327 #312

Removing unnecessary circular karma plugin dependencies. Karma includes the latest version of them. Found here in devDependencies: https://github.com/karma-runner/karma/blob/master/package.json
Added back karma-coverage

npm install and npm test pass (shoutout to @jackhsu978 for pointing out my mistake)
Merge branch 'master' of https://github.com/wspurgin/mean into wspurgin-master