Merge pull request #79 from pveber/papers

Imported "A few papers on ocaml", issue #35
menu: add Papers

Relates to Issue #35.
menu: remove Advanced Tutorials and Papers item

Resolves Issue #17.
companies.html: minor punctuation fix
Add support for comments within comments.
Improve error reporting (error location).
CSS: render keywords (kwa) and the like in "ocamltop-input".
Enable $(ocaml) to include OCaml code from files.
Wrap OCaml code with a ".listing" <span>.
Add syntax highlighting for modules.
Add "ref" as an OCaml keyword.
Syntax highlighting: support for "open" and "module".
Syntax highlighting: add support for "let () =".
Syntax highlighting: add keyword "new".
Add syntax highlighting for some tutorials.
Solve "Truth tables for logical expressions".
Fix the selection of the error location when at the ";;".
Solve "Gray code".
Solve "Construct completely balanced binary trees".
Solve "Symmetric binary trees".