Use inspect/1 instead of to_string/1 on errors

It fixes #26

lib/httpoison/base.ex

@@ -91,7 +91,7 @@ defmodule HTTPoison.Base do
           {:ok, id} ->
             %HTTPoison.AsyncResponse { id: id }
           {:error, reason} ->
-            raise HTTPoison.HTTPError, message: to_string(reason)
+            raise HTTPoison.HTTPError, message: inspect(reason)
          end
       end
 

test/httpoison_base_test.exs

@@ -53,4 +53,15 @@ defmodule HTTPoisonBaseTest do
 
     assert validate :hackney
   end
+
+  test "request raises error tuple" do
+    expect(:hackney, :request, 5, {:error, {:closed, "Something happened"}})
+
+
+    assert_raise HTTPoison.HTTPError, "{:closed, \"Something happened\"}", fn ->
+      HTTPoison.get("http://localhost")
+    end
+
+    assert validate :hackney
+  end
 end

test/httpoison_test.exs

@@ -92,7 +92,7 @@ defmodule HTTPoisonTest do
   end
 
   test "exception" do
-    assert_raise HTTPoison.HTTPError, "econnrefused", fn ->
+    assert_raise HTTPoison.HTTPError, ":econnrefused", fn ->
       HTTPoison.get "localhost:1"
     end
   end