Fix String.contains? not raising on non-string arg
Fix String.contains? not raising on non-string arg

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