Proposing a new implementation for Range encoding

lib/poison/encoder.ex

@@ -329,7 +329,7 @@ defimpl Poison.Encoder, for: List do
   end
 end
 
-defimpl Poison.Encoder, for: [Range, Stream, MapSet, HashSet] do
+defimpl Poison.Encoder, for: [Stream, MapSet, HashSet] do
   alias Poison.Encoder
 
   use Poison.Pretty
@@ -369,6 +369,14 @@ defimpl Poison.Encoder, for: [Date, Time, NaiveDateTime, DateTime] do
   end
 end
 
+defimpl Poison.Encoder, for: Range do
+  alias Poison.Encoder
+
+  def encode(range, options) do
+    Encoder.Map.encode(%{first: range.first, last: range.last}, options)
+  end
+end
+
 defimpl Poison.Encoder, for: Any do
   alias Poison.{Encoder, EncodeError}
 

test/poison/encoder_test.exs

@@ -79,14 +79,23 @@ defmodule Poison.EncoderTest do
   end
 
   test "Range" do
-    assert to_json(1..3) == "[1,2,3]"
+    r1 = 1..10
 
-    assert to_json(1..3, pretty: true) == """
-           [
-             1,
-             2,
-             3
-           ]\
+    assert to_json(r1, pretty: true) == """
+           {
+             "last": 10,
+             "first": 1
+           }\
+           """
+
+    a = 1
+    b = 999_999_999
+
+    assert to_json(a..b, pretty: true) == """
+           {
+             "last": #{b},
+             "first": #{a}
+           }\
            """
   end