add slides of DataAnalysis
add version to 0.3.1
add more dependencies
Merge pull request #14 from JohnsonHsieh/master

Fix error for Mac OS

Thanks :)
update content of ggplot2
update version
Merge pull request #15 from wush978/master

update content of ggplot2
update DA
Merge branch 'master' into feat/add_DA

Conflicts:
	DESCRIPTION
import knitr for non-windows testing
Merge pull request #17 from wush978/hotfix/test-typo

import knitr for non-windows testing
add DA_file API for estate_linux.rds
add libxml2-dev for ubuntu
Merge remote-tracking branch 'twruser/master'
update helper functions for slides
Merge remote-tracking branch 'origin/master' into feat/add_DA
add the version of George
Merge pull request #16 from wush978/feat/add_DA

Feat/add da
debug of typo in helper function
update .gitmodules
Merge pull request #19 from wush978/master

debug of typo in helper function