Add notes about the complexity of ++ and --
Add notes about the complexity of ++ and --

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