Update streaming-stats requirement from 0.1.28 to 0.2.2
Update streaming-stats requirement from 0.1.28 to 0.2.2

Updates the requirements on [streaming-stats](https://github.com/BurntSushi/rust-stats) to permit the latest version.
- [Release notes](https://github.com/BurntSushi/rust-stats/releases)
- [Commits](https://github.com/BurntSushi/rust-stats/compare/0.1.28...0.2.2)
cstorey/phi-accrual-rs