Cluster labels are not visible when cluster has fill color #175
Description
The cluster demo page has labels configured for each node group, but it is not visible due the to group fill color:
g.setNode('group', {label: 'Group', clusterLabelPos: 'top', style: 'fill: #d3d7e8'});
g.setNode('top_group', {label: 'Top Group', clusterLabelPos: 'bottom', style: 'fill: #ffd47f'});
g.setNode('bottom_group', {label: 'Bottom Group', style: 'fill: #5f9488'});
It seems the node order is playing some role on how the elements are shown. I was able to get it to be visible by inspecting and manually editing the generated svg and inverting the rect/g.label element positions:
<g class="cluster" transform="translate(283.0234375,223)" style="opacity: 1;">
<rect style="fill: #d3d7e8" width="435.296875" height="273" x="-217.6484375" y="-136.5"></rect>
<g class="label">
<g transform="translate(-19.0625,-136.5)"><text><tspan xml:space="preserve" dy="1em" x="1">Group</tspan></text></g>
</g>
</g>