added codebook
Merge branch 'master' of https://github.com/johanwasserman/Coursera.git

Conflicts:
	GettingAndCleaningData/README.md
Merge branch 'master' of https://github.com/johanwasserman/Coursera.git

Conflicts:
	GettingAndCleaningData/README.md
Signed-off-by: Johan Waserman <johan.wasserman@gmail.com>