Allow for color bar font size to be changed
Allow for color bar font size to be changed

Address issue #157

Allow for color bar font size for functions that plot fields. This allows
the `fontsize` argument to change all of the font in the plot. Changing
`fontsize` drastically can lead to images that have text overlapping
the image.

davidbrough1/pymks,fredhohman/pymks,davidbrough1/pymks,awhite40/pymks,XinyiGong/pymks