[TASK] Configure Travis for better build performance
[TASK] Configure Travis for better build performance

* set sudo: false to allow usage of their new container-based infrastructure
* enable bundler caching

peterpih/country_select,dgilperez/country_select,scudco/country_select,dhinal41/country_select,cllns/country_select,rposborne/country_select,stefanpenner/country_select