Add examples and polish docs for the Collectable protocol (#5572)
Add examples and polish docs for the Collectable protocol (#5572)


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