code: function( idOrLayer ){
  
              var id = idOrLayer.id ? idOrLayer.id : idOrLayer
                  ,el = this._layers[ id ].el
                  ;
  
              if ( el !== this.el ){
                  el.parentNode.removeChild( el );
              }
              delete this._layers[ id ];
              return this;
          }
docs: CanvasRenderer#removeLayer( id ) -> this
  CanvasRenderer#removeLayer( layer ) -> this
  - id (String): The id for the layer
  - layer (Layer): The layer
  
  Remove a layer.