fix: do not cast string/atom enum values

- enum choices values should be treated as it are
  - strings aren't valid atoms choices:
    `"green" in [:green, :blue, :red]` should be false

lib/peri.ex

@@ -813,7 +813,7 @@ defmodule Peri do
   end
 
   defp validate_field(val, {:enum, choices}, _data) do
-    if to_string(val) in Enum.map(choices, &to_string/1) do
+    if val in choices do
       :ok
     else
       info = [choices: inspect(choices, pretty: true), actual: inspect(val)]

mix.exs

@@ -1,7 +1,7 @@
 defmodule Peri.MixProject do
   use Mix.Project
 
-  @version "0.2.12"
+  @version "0.3.0"
   @source_url "https://github.com/zoedsoupe/peri"
 
   def project do