code: function( contentItem, index ) {
  		var tab = new lm.controls.Tab( this, contentItem );
  		
  		if( this.tabs.length === 0 ) {
  			this.tabs.push( tab );
  			this.tabsContainer.append( tab.element );
  			return;
  		}
  	
  		if( index === undefined ) {
  			index = this.tabs.length;
  		}
  	
  		if( index > 0 ) {
  			this.tabs[ index - 1 ].element.after( tab.element );
  		} else {
  			this.tabs[ 0 ].element.before( tab.element );
  		}
  	
  		this.tabs.splice( index, 0, tab );
  	}
docs: Creates a new tab and associates it with a contentItem
  
  @param   {lm.item.AbstractContentItem} contentItem
  @param   {Integer} index The position of the tab
  
  @returns {void}