Mention Python 3.7 in the docs

Author: mjs

README.rst

@@ -5,7 +5,7 @@ library.
 
 =========================  ========================================
 Current version            2.0.0
-Supported Python versions  2.7, 3.4, 3.5 and 3.6
+Supported Python versions  2.7, 3.4 - 3.7
 License                    New BSD
 Project home               https://github.com/mjs/imapclient/
 PyPI                       https://pypi.python.org/pypi/IMAPClient

doc/src/index.rst

@@ -30,7 +30,7 @@ explains IMAP in detail. Other RFCs also apply to various extensions
 to the base protocol. These are referred to in the documentation below
 where relevant.
 
-Python versions 2.7, 3.4, 3.5 and 3.6 are officially supported.
+Python versions 2.7 and 3.4 through 3.7 are officially supported.
 
 Getting Started
 ---------------

setup.py

@@ -33,7 +33,7 @@
     * Convenience methods are provided for commonly used functionality.
     * Exceptions are raised when errors occur.
 
-Python versions 2.7, 3.4, 3.5 and 3.6 are officially supported.
+Python versions 2.7 and 3.4 through 3.7 are officially supported.
 
 IMAPClient includes comprehensive units tests and automated
 functional tests that can be run against a live IMAP server.