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. Fix RST syntax in HACKING.rst
3. Update moved URLs in README.rst

Change-Id: I74bfead9b1962ad9c5e9eb2f7ab79022566085c9

HACKING.rst

@@ -1,12 +1,12 @@
 Freezer DR Style Commandments
-===========================
+=============================
 
 - Step 1: Read the OpenStack Style Commandments
   https://docs.openstack.org/hacking/latest/
 - Step 2: Read on
 
 Freezer DR Specific Commandments
-------------------------------
+--------------------------------
 
 Logging
 -------
@@ -38,4 +38,4 @@ callable we prefer that the call also uses keyword arg syntax. For example::
     f(0, True)
 
 This gives us the flexibility to re-order arguments and more importantly
-to add new required arguments. It's also more explicit and easier to read.
+to add new required arguments. It's also more explicit and easier to read.

README.rst

@@ -2,8 +2,8 @@
 Team and repository tags
 ========================
 
-.. image:: http://governance.openstack.org/badges/freezer-dr.svg
-    :target: http://governance.openstack.org/reference/tags/index.html
+.. image:: https://governance.openstack.org/tc/badges/freezer-dr.svg
+    :target: https://governance.openstack.org/tc/reference/tags/index.html
 
 .. Change things from this point on
 

test-requirements.txt

@@ -1,6 +1,7 @@
 # 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.
+
 astroid==1.6.5 # LGPLv2.1
 flake8>=2.5.4,<2.6.0  # MIT
 hacking>=0.12.0,!=0.13.0,<0.14  # Apache-2.0
@@ -11,5 +12,6 @@ pylint==1.9.2 # GPLv2
 pyflakes==1.0.0
 stestr>=2.0.0 # Apache-2.0
 testtools>=2.2.0
-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,!=2.1.0,>=1.6.2;python_version>='3.4'  # BSD
 openstackdocstheme>=1.18.1 # Apache-2.0