need to fetch dependencies from `crates.io`

[plebhash]

#11 uses stratum crate versions from stratum-mining/stratum#2098 that have not yet been published to crates.io

as soon as they are published (during v0.1.9 release of that repo), we need to adapt Cargo.toml here to pull deps from crates.io

[plebhash]

stratum repo release v0.1.9 is out: https://github.com/stratum-mining/stratum/releases/tag/v1.9.0

starting work here