use std::path::Path[Buf] and join for paths

[Mackiovello]

$ cargo run -- init myproject/
    Finished dev [unoptimized + debuginfo] target(s) in 0.08s
     Running `target/debug/wasm-pack init myproject/`

  [1/8] Checking crate configuration...
  [2/8] Adding WASM target...
  [3/8] Compiling to WASM...
  [4/8] Creating a pkg directory...
  [5/8] Writing a package.json...
  :-) [WARN]: Field description is missing from Cargo.toml. It is not necessary, but recommended
  :-) [WARN]: Field repository is missing from Cargo.toml. It is not necessary, but recommended
  :-) [WARN]: Field license is missing from Cargo.toml. It is not necessary, but recommended
  [6/8] Copying over your README...
  :-) [WARN]: origin crate has no README
  [7/8] Installing WASM-bindgen...
  [8/8] Running WASM-bindgen...
  :-) Done in 2 minutes
| :-) Your WASM pkg is ready to publish at myproject//pkg.

In the last line it says "Your WASM pkg is ready to publish at myproject//pkg.". It should probably just be "myproject/pkg".

This is on Linux.

[Mackiovello]

The issue is only when the path has a trailing forward slash. Would it make sense to trim this in set_crate_path?

Since we probably have this issue in a number of places where we do {}/pkg, I think that's the way to deal with it.

[fitzgen]

Long term, I think a lot of places should start using std::path::Path[Buf] in wasm-pack, and then we could use the join method instead of {}/pkg.

[ashleygwilliams]

strong agree with @fitzgen. have renamed this issue to that plan. PRs welcome!

[Mackiovello]

PRs welcome!

I'd love to take this one! It seems to be on my level.