Sync Sphinx requirement

1. Sync sphinx dependency with global requirements. It caps python 2 since
sphinx 2.0 no longer supports Python 2.7.
2. Update some URLs to latest
3. Remove unncessary "=="

Change-Id: Idcb616fd3add4d58f22b91865cec8a54fe492092

CONTRIBUTING.rst

 If you would like to contribute to the development of OpenStack, you must
 follow the steps in this page:
 
-   http://docs.openstack.org/infra/manual/developers.html
+   https://docs.openstack.org/infra/manual/developers.html
 
 If you already have a good understanding of how the system works and your
 OpenStack accounts are set up, you can skip to the development workflow
 section of this documentation to learn how changes to OpenStack should be
 submitted for review via the Gerrit tool:
 
-   http://docs.openstack.org/infra/manual/developers.html#development-workflow
+   https://docs.openstack.org/infra/manual/developers.html#development-workflow
 
 Pull requests submitted through GitHub will be ignored.
 

HACKING.rst

 kayobe Style Commandments
-===============================================
+=========================
 
 Read the OpenStack Style Commandments https://docs.openstack.org/hacking/latest/

doc/requirements.txt

+# The order of packages is significant, because pip processes them in the order
+# of appearance. Changing the order has an impact on the overall integration
+# process, which may cause wedges in the gate later.
+
 reno!=2.3.1,>=1.8.0 # Apache-2.0
-sphinx>=1.5.1 # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.4'  # BSD

test-requirements.txt

@@ -11,6 +11,7 @@ hacking>=0.12.0,<0.13 # Apache-2.0
 molecule<3 # MIT
 oslotest>=1.10.0 # Apache-2.0
 # NOTE(mgoddard): This is required by tools/sphinx8.
-sphinx>=1.5.1 # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2,<2.0.0;python_version=='2.7'  # BSD
+sphinx!=1.6.6,!=1.6.7,>=1.6.2;python_version>='3.4'  # BSD
 stestr # Apache-2.0
 yamllint # GPLv3