Call Logger.flush in System.at_exit when running mix test.
Call Logger.flush in System.at_exit when running mix test.

Otherwise messages logged by tests might not show up in the console
which makes finding out why tests failed a lot harder.

gfvcastro/elixir,lexmag/elixir,pedrosnk/elixir,ggcampinho/elixir,antipax/elixir,joshprice/elixir,kimshrier/elixir,michalmuskala/elixir,beedub/elixir,gfvcastro/elixir,elixir-lang/elixir,kimshrier/elixir,beedub/elixir,kelvinst/elixir,lexmag/elixir,pedrosnk/elixir,antipax/elixir,kelvinst/elixir,ggcampinho/elixir