There are a few problems in cargo-binstall where sometimes change to
`Cargo.lock` does not invalidate the cache.

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

This simple mistake caused the entire `Cargo.lock` to be ignored (JS
treats having no return as `false`).

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

The values for the dependencies could be strings intead of objects, so
add a `try` block to take care of that.

Also set `dep.path` to `""` if the dependency contains a key `path` to
make sure that the cache isn't invalidated due to change in workspace.

Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>