ggplot 0.5.1

	* renamed scale_manual to scale_identity to map position_identity and stat_identity
	* ensured all grob consistently named
	* renamed aesthetics argument to mapping to be consistent with description in book
	* added useful utilities for modifying grobs
	* bug fixes to x axis range with interval geoms
	* added ability to turn legend off for single scale (currently undocumented)
	* added economics data set and matching examples


ggplot2 0.5

 * complete rewrite of ggplot code base

 * id/grouping completely rewritten so that automatically grouped when any of the aesthetics is a categorical variable.  This behaviour is defined in the Grammar of Graphics, and makes things like qplot(wt, data=mtcars, geom="density", colour=factor(cyl)) work nicely
