tower-buffer 0.3.0

Buffer requests before dispatching to a `Service`.
Documentation
# 0.3.0 (December 19, 2019)

- Update to `tokio 0.2`
- Update to `futures-core 0.3`
- Update to `tower-service 0.3`
- Update to `tower-layer 0.3`

# 0.3.0-alpha.2 (September 30, 2019)

- Move to `futures-*-preview 0.3.0-alpha.19`
- Move to `pin-project 0.4`

# 0.3.0-alpha.1b (September 13, 2019)

- Remove `Stream` unused warning.

# 0.3.0-alpha.1a (September 13, 2019)

- Fix `poll_next` not exisitng.

# 0.3.0-alpha.1 (September 11, 2019)

- Move to `std::future`

# 0.1.1 (July 19, 2019)

- Add `tracing` support

# 0.1.0 (April 26, 2019)

- Initial release