DOC: Add verbose deprecation to changelog.

Author: tswast

docs/source/changelog.rst

@@ -6,6 +6,7 @@ Changelog
 - Fix bug with querying for an array of floats (:issue:`123`)
 - Fix bug with integer columns on Windows. Explicitly use 64bit integers when converting from BQ types. (:issue:`119`)
 - Update ``google-cloud-python`` dependency to version 0.32.0+. Fixes bug caused by breaking change the way ``google-cloud-python`` handles additional configuration argument to ``read_gbq``. (:issue:`152`)
+-  **Deprecates** the ``verbose`` parameter. Messages use the logging module instead of printing progress directly to standard output. (:issue:`12`)
 
 0.3.1 / 2018-02-13
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