Make Gson adapter explicitly read StringIO object

Author: rwz

lib/multi_json/adapters/gson.rb

@@ -8,6 +8,7 @@ class Gson < Adapter
       ParseError = ::Gson::DecodeError
 
       def load(string, options={})
+        string = string.read if StringIO === string
         ::Gson::Decoder.new(options).decode(string)
       end