Add PDFs of our paper's references (sources)
First outline of paper with content comments

No titles, subtitles, section headers, etc are yet final. Includes
resulting PDF and BibTeX database.
Introduction and first part of Crowdsourcing defined

Abstract still contains dummy text.
First committable version of sections 1 through 4

Still missing: abstract, 5, 6 and conclusion.
Add paper/references/*.pdf to gitignore