.travis.yml in imgkit-1.6.1 vs .travis.yml in imgkit-1.6.2

- old
+ new

@@ -1,5 +1,10 @@
 rvm:
+  - "2.6"
+  - "2.5"
+  - "2.4"
+  - "2.3"
+  - "2.2"
   - "2.1.5"
   - "2.1.4"
   - "2.1.3"
   - "2.1.2"
   - "1.9.3"