Added support for following style properties, Node: z-index. Edge: source-arrow-color, target-arrow-color, z-index.
Added support for following style properties, Node: z-index. Edge: source-arrow-color, target-arrow-color, z-index.

KonstantinShemyak/cytoscape.js,soomin-maeng/cytoscape.js,cytoscape/cytoscape.js,cytoscape/cytoscape.js,rlugojr/cytoscape.js,soomin-maeng/cytoscape.js,KonstantinShemyak/cytoscape.js,rlugojr/cytoscape.js