Remove things that are staying in std::ascii
Remove deprecated stuff.
Make Ascii implement Copy.
v0.1.0

This builds on a Rust compiler that includes https://github.com/rust-lang/rust/pull/19916
Update REAMDE and metadata.
Rename as_str_ascii to as_str.

There is no point in this _ascii suffix.
Add .as_bytes() -> &[u8] to ASCII strings.
Remove to_ascii and into_ascii methods that panic on failure.
Rename to_ascii_opt and into_ascii_opt to to_ascii and into_ascii.
Have to_ascii and into_ascii return Result rather than Option.

This enables using them with try!().

For into_ascii, the Err case also returns the origin String or Vec.
v0.2.0: modernize the API