Update travis build matrix.
Update travis build matrix.

- The version of cucumber I'm locked to doesn't install on 1.9.3.
- Let's try building against rbx and jruby, too.
Shopify/vcr,cemo/vcr,nishanbose/vcr,intfrr/vcr,myronmarston/vcr,myronmarston/vcr,mcfiredrill/vcr,intfrr/vcr,ihassin/vcr,davidbebb/vcr,asymmetric/vcr,chriswoodrich/vcr,ZmagoD/vcr,irfanah/vcr,allyapp/vcr,Shopify/vcr,mcfiredrill/vcr,irfanah/vcr,chriswoodrich/vcr,ZmagoD/vcr,allyapp/vcr,ihassin/vcr,asymmetric/vcr,benjaminoakes/vcr,cemo/vcr,nishanbose/vcr,davidbebb/vcr