Allow to pass css_classes as option to tree.render

[thomasstjerne]

tree.display is not available before tree.render has been called.
In order to use own css_classes you would need to call tree.render twice:

tree.render(options);
tree.display.css(css_classes).update();
tree.render(options);

Better:

tree.render({
            'container': '#phylotreeContainer',
            'max-radius': 468,
            'width': 500,
            'css_classes': {
                'tree-container': 'phylotree-container',
                'tree-scale-bar': 'phylotree-tree-scale-bar',
                 'node': 'phylotree-node'
         }
   });