.travis.yml in gon-6.2.0 vs .travis.yml in gon-6.2.1

@@ -1,6 +1,10 @@
 language: ruby
 sudo: false
+env:
+  - "RABL_GEM=rabl"
+  - "RABL_GEM=rabl-rails"
+
 rvm:
   - 2.3.3
   - 2.4.0
   - ruby-head
 # uncomment this line if your project needs to run something other than `rake`: