impl Debug for Many Types

[nixpulvis]

It would help a lot in learning neon if I could type:

println!("{:?}", call.arguments);
// or even...
println!("{:?}", call);

Types referenced:

• neon::vm::Arguments
• neon::vm::Call

I'm sure there are a few more types that need Debug as well. I'll try to update this list as I find them.

[dherman]

I agree they should implement Debug although I'm not sure how useful we can make the output -- in particular I'm trying to figure out whether it's dangerous to actually touch the JS VM at all. If we can't, then we'd only be able to say some very generic (and not super useful) information like struct Arguments {}.

[kjvalencik]

In addition to Debug, we should eagerly implement other common traits.

https://rust-lang.github.io/api-guidelines/interoperability.html#types-eagerly-implement-common-traits-c-common-traits