Documentation improvements

[Drup]

Should fix #209
cc @fxfactorial

For the oasis part of the question, I oppened ocaml/ocamlbuild#45

[aantron]

You might even want to contrast >> with >>=, since this is what is setting up the expectation in the first place. Note that unlike [>>=], [>>] is not an OCaml value..., or something.

[Drup]

@aantron They are recorded, but it's going to be so mangled it might as well not be the case. I added a slight precision. I also added more pointers to the manual.
Your formulation for >> is better, thanks!

[aantron]

Strange, why aren't there links to comments on outdated diffs?

[aantron]

Looks good, apart from the semicolon in the message for 533ef6f :)