Link to whats new and changelog from PyPI page.

It's a pet peeve of mine when you can't at least directly get to the
changelog for a release from the PyPI page. Before this, it took at
least three clicks and some reading to figure out where they
were.

(Including directly in the page is better, but our notes are kind
of long; maybe we should split them up?)

[skip ci]

README.rst

@@ -18,8 +18,11 @@ simpler implementation and better performance. Read why others `use
 gevent`_ and check out the list of the `open source projects based on
 gevent`_.
 
-gevent is licensed under MIT license.
+gevent is licensed under the MIT license.
 
+See `what's new`_ in the latest major release.
+
+Check out the detailed changelog_ for this version.
 
 Get gevent
 ==========
@@ -128,3 +131,5 @@ CI is used to test on Linux, and `AppVeyor`_ runs the builds on Windows.
 .. _coverage.py: https://pypi.python.org/pypi/coverage/
 .. _coveralls.io: https://coveralls.io/github/gevent/gevent
 .. _AppVeyor: https://ci.appveyor.com/project/denik/gevent
+.. _what's new: http://www.gevent.org/whatsnew_1_1.html
+.. _changelog: http://www.gevent.org/changelog.html