Add release notes for 4.0.1 and update version number.

docs/releases.rst

@@ -4,6 +4,7 @@ Release notes
 .. toctree::
    :maxdepth: 2
 
+   releases/v4.0.1
    releases/v4.0.0
    releases/v3.2.2
    releases/v3.2.1

docs/releases/v4.0.1.rst

@@ -0,0 +1,20 @@
+What's new in Tornado 4.0.1
+===========================
+
+In progress
+-----------
+
+* The build will now fall back to pure-python mode if the C extension
+  fails to build for any reason (previously it would fall back for some
+  errors but not others).
+* `.IOLoop.call_at` and `.IOLoop.call_later` now always return
+  a timeout handle for use with `.IOLoop.remove_timeout`.
+* If any callback of a `.PeriodicCallback` or `.IOStream` returns a
+  `.Future`, any error raised in that future will now be logged
+  (similar to the behavior of `.IOLoop.add_callback`).
+* Fixed an exception in client-side websocket connections when the
+  connection is closed.
+* ``simple_httpclient`` once again correctly handles 204 status
+  codes with no content-length header.
+* Fixed a regression in ``simple_httpclient`` that would result in
+  timeouts for certain kinds of errors.

setup.py

@@ -98,7 +98,7 @@ http://api.mongodb.org/python/current/installation.html#osx
 
 kwargs = {}
 
-version = "4.0"
+version = "4.0.1b1"
 
 with open('README.rst') as f:
     kwargs['long_description'] = f.read()

tornado/__init__.py

@@ -25,5 +25,5 @@ from __future__ import absolute_import, division, print_function, with_statement
 # is zero for an official release, positive for a development branch,
 # or negative for a release candidate or beta (after the base version
 # number has been incremented)
-version = "4.0"
-version_info = (4, 0, 0, 0)
+version = "4.0.1b1"
+version_info = (4, 0, 1, -100)