Add Grunt to automate testing and linting. Add Karma to run tests

Adds grunt to automate tasks. 

The following grunt tasks are added:

grunt jshint: lints the code. (note, this will fail until a .jshintrc file is added, like in PR https://github.com/grevory/angular-local-storage/pull/35)

grunt test: Runs karma tests

grunt: runs jshint task followed by test.


This creates a dependency on nodejs (which FE should have nowadays)
npm install and bower install are needed to install the testing dependencies.