Use poison < 4.0 on Elixir < 1.6 (#419)
Use poison < 4.0 on Elixir < 1.6 (#419)

Poison 4.0.0 uses some new Elixir 1.6 features which won't work on any
Elixir version lower than 1.6. Use a more restrictive version lock for
Elixir < 1.6 to the dependencies list.
appsignal/appsignal-elixir,appsignal/appsignal-elixir,appsignal/appsignal-elixir,appsignal/appsignal-elixir