code: function CommittingEventTransformer (meta, transformFn) {
    Definition.call(this, meta);
  
    meta = meta || {};
  
    if (transformFn && !_.isFunction(transformFn)) {
      var err = new Error('Transform function not injected!');
      debug(err);
      throw err;
    }
  
    this.version = meta.version;
  
    this.transformFn = transformFn;
  }
docs: CommittingEventTransformer constructor
  @param {Object}   meta  Meta infos like: { name: 'name', version: 1 }
  @param {Function} transformFn Fuction handle
  `function(evt, clb){}`
  @constructor