Deprecate this library once Elixir 1.10 is published

[hauleth]

elixir-lang/elixir#9333 removes custom Elixir logger backend handling with Erlang's logger which will cause infinite logging loop with this library if Lager is configured to listen on logger messages (the default).

[whitelynx]

if Lager is configured to listen on logger messages (the default).

Is that actually the default? Everything I've seen (e.g., erlang-lager/lager#519) seems to indicate that Lager doesn't do anything to try to handle logger messages yet. I'd love it if it did, though!

[hauleth]

Indeed, that is not yet a fact.