Major Features
- BokehRunner - [104](https://github.com/prefecthq/prefect/issues/104), [#128](https://github.com/prefecthq/prefect/issues/128)
- Control flow: `ifelse`, `switch`, and `merge` - [92](https://github.com/prefecthq/prefect/issues/92)
- Set state from `reference_tasks` - [95](https://github.com/prefecthq/prefect/issues/95), [#137](https://github.com/prefecthq/prefect/issues/137)
- Add flow `Registry` - [90](https://github.com/prefecthq/prefect/issues/90)
- Output caching with various `cache_validators` - [84](https://github.com/prefecthq/prefect/issues/84), [#107](https://github.com/prefecthq/prefect/issues/107)
- Dask executor - [82](https://github.com/prefecthq/prefect/issues/82), [#86](https://github.com/prefecthq/prefect/issues/86)
- Automatic input caching for retries, manual-only triggers - [78](https://github.com/prefecthq/prefect/issues/78)
- Functional API for `Flow` definition
- `State` classes
- `Signals` to transmit `State`
Minor Features
- Add custom syntax highlighting to docs - [141](https://github.com/prefecthq/prefect/issues/141)
- Add `bind()` method for tasks to call without copying - [132](https://github.com/prefecthq/prefect/issues/132)
- Cache expensive flow graph methods - [125](https://github.com/prefecthq/prefect/issues/125)
- Docker environments - [71](https://github.com/prefecthq/prefect/issues/71)
- Automatic versioning via Versioneer - [70](https://github.com/prefecthq/prefect/issues/70)
- `TriggerFail` state - [67](https://github.com/prefecthq/prefect/issues/67)
- State classes - [59](https://github.com/prefecthq/prefect/issues/59)
Fixes
- None
Breaking Changes
- None