[travis-ci] decrease stack size and increase memory size on JRuby
[travis-ci] decrease stack size and increase memory size on JRuby

... to avoid "unable to create new native thread" fatal failures

cloudvox/adhearsion,renemendoza/adhearsion,renemendoza/adhearsion,cloudvox/adhearsion,adhearsion/adhearsion,adhearsion/adhearsion,cloudvox/adhearsion,adhearsion/adhearsion,cloudvox/adhearsion,adhearsion/adhearsion,renemendoza/adhearsion