Add 2.15 link to docs page
Add 2.15 link to docs page

bmbouter/pulpproject.org,pulp/pulpproject.org,bmbouter/pulpproject.org,bmbouter/pulpproject.org,bmbouter/pulpproject.org,dkliban/pulpproject.org,pulp/pulpproject.org,dkliban/pulpproject.org,pulp/pulpproject.org,dkliban/pulpproject.org,dkliban/pulpproject.org,pulp/pulpproject.org