Land rapid7#3281, require latest Ruby 1.9.3

Note, this will cause developer environments to complain until Ruby is
reinstalled. It's probably a good idea to reinstall anyway, though,
since people who haven't in a while may have been linked against a
Heartbleed-vulnerable openssl library.

Author: Tod Beardsley

.ruby-version

@@ -1 +1 @@
-1.9.3-p484
+1.9.3-p545