Fix the section name in CONTRIBUTING.rst
Fix the section name in CONTRIBUTING.rst

The name of the section 'If you're developer, start here'
has changed in the wiki. This commit updates it to correctly
refer to the good section.

Changed urls to use https

Change-Id: I7cec7b6ec209ae9ad95035dac4c9da4e09d6e0dc
Closes-bug: #1335189

NaohiroTamura/ironic-lib,faizan-barmawer/elytics,citrix-openstack-build/ironic-lib,openstack/ironic-lib,faizan-barmawer/ironic-lib