code: function( functionName, functionArguments, bottomUp, skipSelf ) {
  		var i;
  
  		if( bottomUp !== true && skipSelf !== true ) {
  			this[ functionName ].apply( this, functionArguments || [] );
  		}
  		for( i = 0; i < this.contentItems.length; i++ ) {
  			this.contentItems[ i ].callDownwards( functionName, functionArguments, bottomUp );
  		}
  		if( bottomUp === true && skipSelf !== true ) {
  			this[ functionName ].apply( this, functionArguments || [] );
  		}
  	}
docs: Calls a method recoursively downwards on the tree
  
  @param   {String} functionName      the name of the function to be called
  @param   {[Array]}functionArguments optional arguments that are passed to every function
  @param   {[bool]} bottomUp          Call methods from bottom to top, defaults to false
  @param   {[bool]} skipSelf          Don't invoke the method on the class that calls it, defaults to false
  
  @returns {void}