v0.12.0

Compatability

• No longer support Elixir 1.4, Elixir 1.5, or Erlang/OTP 19 (minumum tested compatiblity is now Elixir 1.6 and Erlang/OTP 20)
• Support Elixir 1.9 and Erlang/OTP 22

Fixes

• Update to Rustler v0.21, which supports Erlang/OTP 22 (but requires a minumum Elixir version of 1.6)