release jruby gem

[andreaseger]

Although it seems you're supporting jruby by e.g. testing against it on travis and adding special handling to some bits of the code for it you have not released a java gem for gemstash. https://rubygems.org/gems/gemstash

This will cause bundler to try installing sqlite3 which won't work on jruby as it has native extensions.

This line won't be evaluated on gem usage but when the gem is build https://github.com/bundler/gemstash/blob/master/gemstash.gemspec#L48