This commit replaces the `slog` family of crates used by `wasm-pack`
with the `log` crate plus `env_logger`. This also means that by default
`wasm-pack` also won't create a `wasm-pack.log` file in the current
directory. Enabling logging will now be done through
`RUST_LOG=wasm_pack` instead of `-v` flags.
Closes#425
This lets us leverage `cargo` for semver finding and then ensure that we get the
exact same version of the CLI that cargo selected. It also lets us support fuzzy
dependencies like "0.2" instead of exact dependencies like "0.2.21" again.
If a test is going to do a potentially destructive operation, instead of
mutating shared fixtures, it should copy the fixture to its own unique directory
and then mutate that copy (doesn't this sound like Rust's borrowing and
ownership rules?! ^.^)
Ashley Williams