Fix an example (didn't work with latest Elixir)
Fix an example (didn't work with latest Elixir)

parkerl/xelixir,cezarykosko/xelixir,elasticdog/xelixir,henrik/xelixir,Egogre/xelixir,wobh/xelixir,tjcelaya/xelixir,victorlcampos/xelixir,montague/xelixir,exercism/xelixir