1. Sync sphinx dependency with global requirements. It caps python 2 since
sphinx 2.0 no longer supports Python 2.7.
2. Remove unncessary "=="
Change-Id: I3ba06e23519177c05352b97c42dd95d2674d5b0a
Update URLs according to OpenStack document migration.
BTW: Do some optimization as well (http -> https)
Change-Id: I9ea1acd93f983bbd74f49a07e4781cc336605f4f
The second section description in CONTRIBUTING.rst is not precise,
we can describe it like other project like nova and cinder.
Change-Id: I9f9f9fa38d190395c80c0101dbfe282de41c948b
Closes-Bug: #1646028