Re-add ChangeLog

One of PBR's features is ChangeLog generation, so it only makes
sense that we would include PBR's ChangeLog in published
documentation too. (Also publishing a ChangeLog is helpful.)

Change-Id: Ie1561c0852dfc6731c29e9202f74f0e4c4b08786

README.rst

@@ -34,6 +34,7 @@ them as quickly as possible.
 * Documentation: https://docs.openstack.org/pbr/latest/
 * Source: https://opendev.org/openstack/pbr
 * Bugs: https://bugs.launchpad.net/pbr
+* ChangeLog: https://docs.openstack.org/pbr/latest/user/history.html
 
 .. _d2to1: https://pypi.python.org/pypi/d2to1
 .. _distutils2: https://pypi.python.org/pypi/Distutils2

doc/source/user/history.rst

@@ -0,0 +1 @@
+.. include:: ../../../ChangeLog

doc/source/user/index.rst

@@ -9,3 +9,4 @@
    packagers
    semver
    compatibility
+   history

tox.ini

@@ -27,6 +27,7 @@ deps =
 commands =
   rm -rf doc/build doc/source/reference/api
   sphinx-build -W -b html doc/source doc/build/html {posargs}
+usedevelop = False
 
 [testenv:releasenotes]
 whitelist_externals = rm