Takes an Elixir value and converts it into a Dynamo-style map.

MapSet.new [1,2,3] |> Elixir.ExAws.Dynamo.Encoder.encode
#=> %{"NS" => ["1", "2", "3"]}

MapSet.new ["A","B","C"] |> Elixir.ExAws.Dynamo.Encoder.encode
#=> %{"SS" => ["A", "B", "C"]}

"bubba" |> ExAws.Dynamo.Encoder.encode
#=> %{"S" => "bubba"}

This is handled via the ExAws.Dynamo.Encodable protocol.