Reword 9.1+2.0 suggestions

Frederik's testing showed 9.1+2.0 is substantially faster than 8.4+1.5, so word the paragraph stronger. At this point 8.4+1.5 is old and 8.4 will reach EOL in July 2014.
Merge pull request #113 from pnorman/patch-4

Reword 9.1+2.0 suggestions