Gauge colour as a gradient memory leak? #49

Seems to be a big performance issue with setting gradients on gauges.

This is how the browser splits its time, the 50% usage on the DOM function is reduced to a few percentage points after the gradient is removed.

daq.Gauge(
                color={"gradient":False,"ranges":{"#00998c":[0,6],"#E09A4F":[6,8],"#E0554E":[8,10]}},
                showCurrentValue=True,
)

Versions:
dash==0.39.0
dash-auth==1.3.2
dash-core-components==0.44.0
dash-daq==0.1.5
dash-html-components==0.14.0
dash-renderer==0.20.0
dash-table==3.6.0
Flask==1.0.2
Flask-Compress==1.4.0
Flask-SeaSurf==0.2.2
plotly==3.7.1

Browser: Firefox 67.0.1