install.packages("devtools")
library(devtools)
dev_mode(on=T)
install_github("hadley/ggplot2")
# use dev ggplot2 now
# when finished do:
dev_mode(on=F) #and you are back to having stable ggplot2
ref: http://stackoverflow.com/questions/9656016/how-to-install-development-version-of-r-packages-github-repository
happy hackin'
