main
remove pdfs, normalize readme format [fix PR#540]
Update link as old one no longer exists (#814)
add specializing ruby paper (#700)
Update README.md
Add the Sketch-n-Sketch paper (#412)
restore link to "The History of Erlang"
Fix broken haskell paper link (#752)
Move languages into languages dir. Move 'tdd' dir into testing (#403)
Rename "paradigm" and "plt" folders for findability (#561)
On the Expressive Power of Programming Languages (#553)