Added colorbars to example in Columnar_Data tutorial
Added colorbars to example in Columnar_Data tutorial

basnijholt/holoviews,ioam/holoviews,vascotenner/holoviews,basnijholt/holoviews,basnijholt/holoviews,ioam/holoviews,vascotenner/holoviews,ioam/holoviews,vascotenner/holoviews