Use Logger instead of :error_logger

[antedeguemon]

This library currently adds a hook to Erlang's :error_logger when the use_logger flag is enabled (at this line). But since Elixir 1.7, Logger is the preferred way of hooking into error logs (see Erlang/OTP logger integration section here).

As Elixir ~> 1.8 is already required by this library, I think it should move towards Logger hooking instead.

[antedeguemon]

Ooops, there is already a pull request for that - #118.

I will leave the issue open while the PR isn't merged. Maintainers, please feel free to close this issue if it is not adequate.