Update libs and dep versions to use cabin >= 0.6.0 and avoid conflicting
0.5 and 0.6 installs. (LOGSTASH-1497)

This was observed as a result of ugprading to jruby 1.7.5 (thus
upgrading rubygems). I believe the order of operations in dependency
resolution was changed to trigger this. Basically, ftw wants cabin>0,
logstash wanted cabin=0.5.0, and if ftw is satisfied first then
logstash's dep fails.
Merge pull request #735 from logstash/fix-cabin-deps

Update libs and dep versions to use cabin >= 0.6.0 and avoid conflicting