tower: prepare to release v0.4.4 (tower-rs#539)

tower: prepare to releasse v0.4.3 (tower-rs#528)

I also fixed up the changelog entries for v0.4.2 while I was here.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

layer: prepare to release v0.3.1 (tower-rs#513)

* layer: prepare to release v0.3.1

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

* whitespace

tower: prepare to release 0.4.1 (tower-rs#514)

* tower: prepare to release 0.4.1

This branch updates the tower-layer dependency to 0.3.1 and prepares a
new release of `tower`. This should fix the broken re-exports of
`layer_fn` and get us a successful docs.rs build.

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

test: update tower-test to v0.4 (tower-rs#512)

Signed-off-by: Eliza Weisman <eliza@buoyant.io>

util: prepare 0.3.1 release (tower-rs#428)

0.3.1 (January 17, 2020)

- Allow opting out of tracing/log (tower-rs#410).

util: Remove dev dep on tower (tower-rs#401)

* util: Remove dev dep on tower

* Fix rustc bug

* enable call-all by default

Prepare limit 0.1.1 release (tower-rs#359)

Prepare buffer 0.1.2 release (tower-rs#360)