[replace] is deprecated

[digama0]

https://github.com/rust-lang/edition-guide/blob/master/src/rust-2018/cargo-and-crates-io/replacing-dependencies-with-patch.md says "we don't intend to deprecate or remove [replace]" but the cargo documentation says it is deprecated.

[ehuss]

Closing per #232, this section has been removed. Indeed, [patch] is preferred over [replace].