Add legend to colormap on Hitmap

[mtog]

Need to add legend. @timeu did you use quantiles? What would be the most appropriate legend?

[timeu]

The color bands are calculated using quantiles because the scores range from 5 - 116 and only a few very significant associations will lead to a non uniformily distributed coloring. However as a future extension we could implement a select box and allow the user to choose from different color methods (linear, quantiles, log, etc). The color legend is displayed below the hitmap