UPGRADE.md in quandl_data-1.3.6 vs UPGRADE.md in quandl_data-1.3.7

@@ -1,4 +1,9 @@
+## 1.3.7
+
+* revise Quandl::Data#frequency to use Quandl::Babelfish.guess_frequency
+
+
 ## 1.3.6
 
 * Add #guess_csv_delimiter to Data::Format.
 
 
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