Remove application source and dependencies using NPM lib.

@param {String} app App to fetch from NPM.
@param {Function} callback Callback to run once work is done.
function (app, callback) {
    var options = {
      dir: configHelpers.getModulesPath(),
      prefix: ''
    };
    npm.load(options, function () {
      npm.commands.uninstall([app], callback);
    });
  }