Fixes YAML serialization/deserialization for Faraday::Utils::Headers

Fixes #690

lib/faraday/utils.rb

@@ -10,12 +10,22 @@ def self.from(value)
         new(value)
       end
 
+      def self.allocate
+        new_self = super
+        new_self.initialize_names
+        new_self
+      end
+
       def initialize(hash = nil)
         super()
         @names = {}
         self.update(hash || {})
       end
 
+      def initialize_names
+        @names = {}
+      end
+
       # on dup/clone, we need to duplicate @names hash
       def initialize_copy(other)
         super
@@ -115,14 +125,6 @@ def parse(header_string)
           }
       end
 
-      def init_with(coder)
-        @names = coder['names']
-      end
-
-      def encode_with(coder)
-        coder['names'] = @names
-      end
-
       protected
 
       def names

test/utils_test.rb

@@ -91,6 +91,8 @@ def test_headers_yaml_roundtrip
 
     assert result.include?('user-agent'), 'Unable to hydrate to a correct Headers'
     assert result.include?('content-type'), 'Unable to hydrate to a correct Headers'
+    assert result['user-agent'] == 'safari', 'Unable to access rehydrated Headers'
+    assert result['content-type'] == 'text/html', 'Unable to access rehydrated Headers'
   end
 end