Add ruby 1.9.3-p429, make it default for 1.9.3

http://www.ruby-lang.org/en/news/2013/05/14/ruby-1-9-3-p429-is-released/

A colleague told me that Travis doesn't support p429 yet. So maybe you don't want p429 as the default for 193, but here it is anyway, just in case.