resizingTextGrob: Adds text grob that scales with viewport size
Description
Creates a new grob class called resizingTextGrob that is supposed to resize automatically
It is a thin layer over grid::textGrob.
Usage
resizingTextGrob(...)
Details
Taken from: http://ryouready.wordpress.com/2012/08/01/creating-a-text-grob-that-automatically-adjusts-to-viewport-size/