.travis.yml in api-auth-1.5.0 vs .travis.yml in api-auth-2.0.0

@@ -1,6 +1,7 @@
 language: ruby
 sudo: false
+cache: bundler
 rvm:
   - 1.8.7-p374
   - 1.9.3
   - 2.1.5
   - 2.2.1