typo
Merge pull request #12 from wush978/hotfix/readme

typo
Merge pull request #13 from wush978/master

add testKnit, slides of Vis
Fix error for Mac OS
Merge pull request #14 from JohnsonHsieh/master

Fix error for Mac OS

Thanks :)
Merge pull request #15 from wush978/master

update content of ggplot2
import knitr for non-windows testing
Merge pull request #17 from wush978/hotfix/test-typo

import knitr for non-windows testing
add libxml2-dev for ubuntu
Merge remote-tracking branch 'twruser/master'