Merge pull request #71 from mjio/fix_serializable_module

Fix method name to convert binary to hex in Serializable module

lib/rbnacl/serializable.rb

@@ -9,7 +9,7 @@ def to_str; to_bytes; end
     #
     # @return [String] a string representing this key
     def inspect
-      "#<#{self.class}:#{Util.bytes2hex(to_bytes)[0,8]}>"
+      "#<#{self.class}:#{Util.bin2hex(to_bytes)[0,8]}>"
     end
   end
 end