Add PDF handling

[uuuser-name]

Add a way for the users to feed a pdf, allows them to select which pages they want to program to create questions on, and automatically extract, consume, and create questions on these pages.
Useful for textbooks and papers.

see #8 for the same idea, but with web-scraping.

[thiswillbeyourgithub]

I did it for you, I intend to add it as a PR in the coming weeks.

[thiswillbeyourgithub]

done in the latest revision

[paulbricman]

@thiswillbeyourgithub addressed this in #15, but the repo still needs some polishing.