ENH: make covariate model work with new and old pandas
BOOK: tweaks
Merge branch 'master' of https://github.com/peterhm/gbd
BUG: paths etc updates to get refactored book graphics to run
bug: validate_age_group can now be imported
enh: add show() to all graphics files
bug: win v cluster load data
rename applications to graphics for all pdfs
graphics folder added
enh: all graphics in book/graphics folder