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: I48206450371b557f51b0842976d48c9042173df2

CONTRIBUTING.rst

@@ -1,14 +1,14 @@
 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.
 

doc/source/contributor/index.rst

@@ -1,6 +1,6 @@
-===========================
- Contributor Documentation
-===========================
+=========================
+Contributor Documentation
+=========================
 
 .. toctree::
    :maxdepth: 2

doc/source/index.rst

@@ -4,7 +4,7 @@
    contain the root `toctree` directive.
 
 Welcome to os-service-types's documentation!
-========================================================
+============================================
 
 Contents:
 

test-requirements.txt

@@ -6,7 +6,8 @@ hacking>=1.1.0,<1.2.0 # Apache-2.0
 
 coverage!=4.4,>=4.0 # Apache-2.0
 python-subunit>=1.0.0 # Apache-2.0/BSD
-sphinx!=1.6.6,!=1.6.7,>=1.6.2 # 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>=2.0.0 # Apache-2.0
 oslotest>=3.2.0 # Apache-2.0
 testscenarios>=0.4 # Apache-2.0/BSD