Merge branch 'rm-depr-forum-promolink' into 'master'

Substituted deprecated forum link with project issues link.

Within the promo partial template we had a Requests link to the
deprecated Forum which is now directing to the project's Issue page.

See merge request !2255

app/views/shared/_promo.html.haml

 .gitlab-promo
   = link_to 'Homepage', promo_url
-  = link_to "Blog", promo_url + '/blog/'
-  = link_to "@gitlab", "https://twitter.com/gitlab"
-  = link_to "Requests", "http://feedback.gitlab.com/"
+  = link_to 'Blog', promo_url + '/blog/'
+  = link_to '@gitlab', 'https://twitter.com/gitlab'
+  = link_to 'Requests', 'https://gitlab.com/gitlab-org/gitlab-ce/blob/master/CONTRIBUTING.md#feature-proposals'