Removed the documentation build instructions
Removed the documentation build instructions

We don't need asciidoc anymore, the documentation build is now
self-contained with Maven and AsciiDoctor.

Along the way I also removed an outdated notice on JDK requirements.

k33g/golo-lang,jnizet/golo-lang,rlespinasse/golo-lang,danielpetisme/golo-lang,k33g/golo-lang,rlespinasse/golo-lang,golo-lang/golo-lang,danielpetisme/golo-lang,rlespinasse/golo-lang,danielpetisme/golo-lang,golo-lang/golo-lang,jnizet/golo-lang,rlespinasse/golo-lang,k33g/golo-lang,jnizet/golo-lang,golo-lang/golo-lang,k33g/golo-lang