The args() and args_os() docs include a line about how the first element
is usually the program name. Include that line in the struct docs too.

… r? @steveklabnik

…frewsxcv

add unstable book to the bookshelf

r? @frewsxcv @GuillaumeGomez

…xcrichton

Extract nomicon to its own repo

part of rust-lang#39588

same as rust-lang#40213 but for the nomicon

r? @alexcrichton

Issue rust-lang#39688 - Help people find String::as_bytes() for UTF-8

Added in links for the inverse functions so people will know that as_bytes() is the inverse of from_utf8() and vice versa.
?r @steveklabnik

Fix description of closure coercion feature

Thanks to @whitequark for pointing this out.

clarify docs for Args and ArgsOs

The args() and args_os() docs include a line about how the first element
is usually the program name. Include that line in the struct docs too.

Fix text formatting in README

There was a missing backtick in the README.

Remove extra space in test description (of a mod test)

Fix a typo in the docs