Add more info on invoking Erlang methods to the README.
Add more info on invoking Erlang methods to the README.

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