Update Rubygems on Travis
Update Rubygems on Travis

https://github.com/travis-ci/travis-ci/issues/8969

BetaNYC/citygram-nyc,codeforamerica/citygram,BetaNYC/citygram-nyc,codeforamerica/citygram,codeforamerica/citygram,codeforamerica/citygram,BetaNYC/citygram-nyc,BetaNYC/citygram-nyc