property updates for previous backported commit

git-svn-id: file:///home/xapian-svn/xapian/branches/1.2@18290 6b2f1b92-a4f3-0310-943f-de3cbe41748b
Backport change from trunk:
README: Note that Ruby 2.1 works too.

git-svn-id: file:///home/xapian-svn/xapian/branches/1.2@18291 6b2f1b92-a4f3-0310-943f-de3cbe41748b