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
Alex Crichton
35fe250d09