Merge pull request #1 from rdpeng/eda

Final ggplot2 part 2 slide fixed
final fixes to ggplot2 -- both parts 1 and 2
fixed one fig in ggplot2_p2
fixed fig.width on 3 plot slide in ggplot2_p1
final plot fix in ggplot2_p2
Merge pull request #45 from ncarchedi/master

ggplot lectures converted from powerpoint to slidify