more work on lit. review
updated mooc lit. review

Merge branch 'master' of github.com:whynotyet/MOOC_dropout

Conflicts:
	dropout.bib
	paper_v1.Rnw
	paper_v1.bbl
	paper_v1.log
	paper_v1.pdf
	paper_v1.synctex.gz
	paper_v1.tex