Hover legend and interactive legend

Added examples of both a hoverLegend and interactiveLegend. The interactiveLegend could possibly replace both toggleLegend and hoverLegend, but at the moment, it feels a bit clunky, since all I did was copy code over to that class. 
rather than nesting everything inside a block, maybe just do
`if (!this._isSetup) {
  return;
}`