Use Exponential Scale for Shard Size Heat Map
Use Exponential Scale for Shard Size Heat Map

According to Fechner's law subjectively perceived brightness is
proportional to the logarithm of the physical luminance of a color. Knowing
that it’s better to use an exponential scale when producing the colors for
the heat map so that differences are brought out more.

Props to @gibrown for the idea.

xyu/elasticsearch-whatson,xyu/elasticsearch-whatson