v0.9.9

Faster cohorts detection, property tests, and a beta quality implementation of scans (nancumsum, ffill, bfill)

What's Changed

• Property tests with hypothesis by @dcherian in #348
• Add scans by @dcherian in #370
• Optimize for-loop merging of cohorts. by @dcherian in #378

Full Changelog: v0.9.8...v0.9.9