Add a title to news headline links.
Fix the "Streams" tutorial so it displays.

All `tryocaml` were also changed to `ocamltop`.
Fixes https://github.com/ocaml/ocaml.org/issues/340
Remove all ```tryocaml

On the way mane code blocks were also corrected.
Fixes https://github.com/ocaml/ocaml.org/issues/282