Derived Display doesn't handle width and alignment parameters

[therustmonk]

For struct like:

#[derive(Display)]
enum Type {
    One,
    Two,
}

The call:

println!("_ {:<20} _", Type::One);

Will print:

_ One _

But this expected:

_ One                 _

The workaround today only to convert it to string first:

println!("_ {:<20} _", Type::One.as_ref()); // and derive `AsRefStr` for enum needed

[Peternator7]

I didn't realize those parameters were exposed. Are you interested in working on this? If not, I'm going to mark this as help-wanted, and see if someone wants to fix it more quickly than I can get around to it.

For anyone interested in working on this. Display::fmt takes a Formatter argument that contains information about the requested padding and alignment. We need to add logic to read that and then pad the outputs accordingly before writing them.

[Peternator7]

I took a look into this over the weekend, and it's actually a pretty small fix. The fmt module exposes a method for formatting strings already so it was as easy as hooking into that. #95