Remove Validations deprecation code

The `ActiveResource::Validations#from_json` method emits deprecation
warnings when handling error response payloads that resemble the
following:

```
{"errors":["First cannot be empty"]}

{"first":["cannot be empty"]}
```

The deprecation was originally introduced in [c643605][] (Feb 4, 2012).
This commit removes documentation mentions of backwards-compatibility
along with the conditional branches that emit the deprecation warnings.

The removal of the backwards support is a breaking change.

[c643605]: c643605

Author: seanpdoyle

lib/active_resource/base.rb

@@ -325,15 +325,6 @@ module ActiveResource
   #   ryan.errors.invalid?(:first)  # => true
   #   ryan.errors.full_messages     # => ['First cannot be empty']
   #
-  # For backwards-compatibility with older endpoints, the following formats are also supported in JSON responses:
-  #
-  #   # {"errors":['First cannot be empty']}
-  #   #   This was the required format for previous versions of ActiveResource
-  #   # {"first":["cannot be empty"]}
-  #   #   This was the default format produced by respond_with in ActionController <3.2.1
-  #
-  # Parsing either of these formats will result in a deprecation warning.
-  #
   # Learn more about Active Resource's validation features in the ActiveResource::Validations documentation.
   #
   # === Timeouts

lib/active_resource/validations.rb

@@ -53,21 +53,8 @@ def from_hash(messages, save_cache = false)
     # Grabs errors from a json response.
     def from_json(json, save_cache = false)
       decoded = ActiveSupport::JSON.decode(json) || {} rescue {}
-      if decoded.kind_of?(Hash) && (decoded.has_key?("errors") || decoded.empty?)
-        errors = decoded["errors"] || {}
-        if errors.kind_of?(Array)
-          # 3.2.1-style with array of strings
-          ActiveResource.deprecator.warn("Returning errors as an array of strings is deprecated.")
-          from_array errors, save_cache
-        else
-          # 3.2.2+ style
-          from_hash errors, save_cache
-        end
-      else
-        # <3.2-style respond_with - lacks 'errors' key
-        ActiveResource.deprecator.warn('Returning errors as a hash without a root "errors" key is deprecated.')
-        from_hash decoded, save_cache
-      end
+      errors = decoded["errors"] || {}
+      from_hash errors, save_cache
     end
 
     # Grabs errors from an XML response.

test/cases/base_errors_test.rb

@@ -111,40 +111,6 @@ def test_should_mark_as_invalid_when_content_type_is_unavailable_in_response_hea
     end
   end
 
-  def test_should_parse_json_string_errors_with_an_errors_key
-    ActiveResource::HttpMock.respond_to do |mock|
-      mock.post "/people.json", {}, %q({"errors":["Age can't be blank", "Name can't be blank", "Name must start with a letter", "Person quota full for today.", "Phone work can't be blank", "Phone is not valid"]}), 422, "Content-Type" => "application/json; charset=utf-8"
-    end
-
-    assert_deprecated(/as an array/, ActiveResource.deprecator) do
-      invalid_user_using_format(:json) do
-        assert @person.errors[:name].any?
-        assert_equal [ "can't be blank" ], @person.errors[:age]
-        assert_equal [ "can't be blank", "must start with a letter" ], @person.errors[:name]
-        assert_equal [ "is not valid" ], @person.errors[:phone]
-        assert_equal [ "can't be blank" ], @person.errors[:phone_work]
-        assert_equal [ "Person quota full for today." ], @person.errors[:base]
-      end
-    end
-  end
-
-  def test_should_parse_3_1_style_json_errors
-    ActiveResource::HttpMock.respond_to do |mock|
-      mock.post "/people.json", {}, %q({"age":["can't be blank"],"name":["can't be blank", "must start with a letter"],"person":["quota full for today."],"phone_work":["can't be blank"],"phone":["is not valid"]}), 422, "Content-Type" => "application/json; charset=utf-8"
-    end
-
-    assert_deprecated(/without a root/, ActiveResource.deprecator) do
-      invalid_user_using_format(:json) do
-        assert @person.errors[:name].any?
-        assert_equal [ "can't be blank" ], @person.errors[:age]
-        assert_equal [ "can't be blank", "must start with a letter" ], @person.errors[:name]
-        assert_equal [ "is not valid" ], @person.errors[:phone]
-        assert_equal [ "can't be blank" ], @person.errors[:phone_work]
-        assert_equal [ "Person quota full for today." ], @person.errors[:base]
-      end
-    end
-  end
-
   private
     def invalid_user_using_format(mime_type_reference)
       previous_format = Person.format