update gantry to v4.1.3

Release Notes - Gantry Joomla Framework - Version 4.1.3

Bug
• Alias menu item type giving 404 error in iphone view (on the pre-responsive templates)
• intro image float fails in j3
• Error loading component com_rokgallery showing up in gantry admin
• Issues with max width and third party google map extensions
• Fontend system messages dont close
• Display issues with select extensions and bootstrap styling

New Feature
• Added custom Gantry overrides support with base set of overrrides