Corrects the second R subset instruction on slide 16

Corrects the second R subset instruction on slide 16 and the erroneous
output (the observation heights=192.3) by recompiling the slides.
Adding library load for slidify
Merge pull request #7 from ajalexander/master

Adding missing library call in README
Merge pull request #5 from jpoliv/master

representingDataR: slide 16: second subset example: wrong instruction and output
Organized lectures by week, added week2 lectures, created folder for pdfs