[rubygems] Jruby 1.7.17-SNAPSHOT

this needs some fixes on the jruby side so it is still WIP

until jruby fixes things we are stuck with jruby-1.7.12
OK - hey my intention was to wait for the release and put the changes somewhere. I guess I should have left them on a local branch or on my repo only. but it is declared as WIP - thought that is enough.