Fixes #6272/BZ1118479 - update Katello links to new JS guide.

Update links in Katello to point to the Javascript style guide.
These links will point to the github files themselves for now
and will be updated once the docs site is live.

http://projects.theforeman.org/issues/6272
https://bugzilla.redhat.com/show_bug.cgi?id=1118479
Yea, .md ought to be the standard extension. I think some files got created by accident with mkd.