Added simple example configuration to readme

Added link to Gruntfile where complete set of example configuration is found + simple configuration to get started without having to guess typical set of required options not browsing project sources.

I had some problems to get task working with only guidance of readme.md.  After short googling and finding https://github.com/angular-translate/grunt-angular-translate/issues/7 I found information what I needed. I thought it would be helpful to have this information directly in Readme.md