return state_code instead of alias state

lib/geocoder/results/opencagedata.rb

@@ -36,12 +36,13 @@ module Geocoder::Result
       @data['components']['village']
     end
 
-
     def state
       @data['components']['state']
     end
 
-    alias_method :state_code, :state
+    def state_code
+      @data['components']['state_code']
+    end
 
     def postal_code
       @data['components']['postcode'].to_s

test/fixtures/opencagedata_madison_square_garden

@@ -49,6 +49,7 @@
             "city": "New York City",
             "stadium" : "Madison Square Garden",
             "state" : "New York",
+            "state_code" : "NY",
             "state_district" : "New York City"
          },
          "confidence" : 10,
@@ -70,4 +71,4 @@
    },
    "total_results" : 1,
    "we_are_hiring" : "http://lokku.com/#jobs"
-}
\ No newline at end of file
+}