Test env for the frontend app

[Lukasz Bandzarewicz]

see 445f55c#commitcomment-4830187
and https://github.com/mathiasbynens/grunt-template
and http://www.ng-newsletter.com/advent2013/#/day/5

// Gruntfile
var env = process.env.ENV || 'development';

var config = require('./config/' + env + '.json');

grunt.initConfig({
  // ...

  'template': {
    'config': {
      'options': {
        data: config
      }
    },
    'files': {
      // The .tmp destination is a yeoman
      // default location. Set this dest
      // to fit your own needs if not using
      // yeoman
      '.tmp/scripts/config.js': 
        ['src/config.js.tpl']
    }
  }
  // ...
});

grunt.loadNpmTasks('grunt-template');
grunt.registerTask('default', ['template']);

ENV=production grunt build