Fix warning introduced by OCaml 4.02.
Update README

Add a section about installing EasyCrypt dependencies/provers directly
from opam.
README: blurb about `opam switch`
doc: keywords generation + common lstlisting mode.
Merge branch '1.0' of git://ci.easycrypt.info/easycrypt into 1.0
"update" compiles the documentation
Missing eol at eof