Clean up some awkward wording around the +spp flag.

This issue was pointed out by lpgauth in #erlounge. While the intention is
clear, the original wording was a bit dodgy. I'm no grammarian--though I am a
native speaker--so it's quite possible the new wording I've introduced is not
impeachable. Should be idiomatic, though.

Signed-off-by: Brian L. Troutwine <brian.troutwine@adroll.com>