update bootstrap.sh : add more ruby versions
update bootstrap.sh : add more ruby versions

cmu-db/cmdbac,cmu-db/cmdbac,cmu-db/db-webcrawler,cmu-db/db-webcrawler,cmu-db/db-webcrawler,cmu-db/cmdbac,cmu-db/cmdbac,cmu-db/db-webcrawler,cmu-db/cmdbac,cmu-db/db-webcrawler