code: function getFields(collection) {
  
      var message = 'What fields should "' + collection + '" have?\n',
          config;
  
      config = {
          properties: {
              fields: {
                  description: message.magenta +
                  '   Comma-separated fieldname:fieldtype pairs (ex: id:index, username:username)\n'.grey,
                  type: 'string',
                  required: true,
                  pattern: FIELDS_REGEXP
              }
          }
      };
  
      prompt.start();
      prompt.message = '   >> ';
      prompt.delimiter = '';
  
      return new Promise(function(resolve, reject) {
          prompt.get(config, function(err, result) {
              if (err) return reject(err);
              return resolve(result.fields);
          });
      }).then(function(input) {
          return (input.match(FIELDS_REGEXP) || []).reduce(function(prev, curr) {
              var parts = curr.split(':');
              prev[parts[0]] = parts[1].replace(/\+/g, '}~{'); // with "+" also support name={fistName}~{lastName} concatenations
              return prev;
          }, {});
      });
  }
docs: Prompt for collection fields.
  @return {Promise}