This commit fixes an issue where if a library is renamed via the `name`
key in the `[lib]` section of the manifest then `wasm-pack` would try to
generate bindings for an noexistent wasm-file, generating an error.
The fix was to internally use `cargo_metadata` more aggressively and
move around where this data is generated. This ended up refactoring a
few locations, but this should also bring improved error messages for
`cargo metadata` as well as caching the resulting data more aggressively
to avoid recalculating it too much.
Closes#339
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.
Alex Crichton