Compared to 1.5.2:

* Compatible with OTP versions from 21 to 25
* Configuration is expected to be `map` by default (proplists supported, but not recommended)
* API to query pool utilization
* API to get pids of all pools belonging to a group
* GitHub CI (unit tests, proper tests, cover, hot upgrade tests, dialyzer)
* Microbenchmarks
* Optimizations (maps instead of `dict`, worker starter optimized)
* Code formatter
* Uses `pg` instead of `pg2` on OTP-23+
* Workers are stopped via `supervisor:terminate_child/2`, not `exit/2`

1.5.2

rebar3 conversion

1.5.0

* Switch from `erlang:now/0` to `os:timestamp/0` to address
  compatibility with Erlang 18.

* New optional config `stop_mfa` allows customization of member
  termination