.travis.yml in declarative-0.0.10 vs .travis.yml in declarative-0.0.20

- old
+ new

@@ -1,8 +1,12 @@
 language: ruby
+before_install: gem install bundler
+cache: bundler
 rvm:
-  - 2.3.1
-  - 1.9.3
-gemfile:
-  - Gemfile
-before_install:
-  - gem install bundler
+  - ruby-head
+  - 2.7
+  - 2.6
+  - 2.5
+  - 2.4
+jobs:
+  allow_failures:
+    - rvm: ruby-head