(maint) update travis for better coverage of in-flight puppet versions

This adds cells for all currently active puppet development versions from
git, and updates the utility cells to a more current ruby. PUP-9356 would
have been detected earlier if we had had these cells in place.

Author: DavidS

.travis.yml

@@ -28,9 +28,9 @@ matrix:
         bundler: true
         directories: ~/.rvm
       before_install: rvm use jruby-9.1.9.0 --install --binary --fuzzy
-    - rvm: 2.4.3
+    - rvm: 2.5.1
       env: CHECK=rubocop
-    - rvm: 2.4.3
+    - rvm: 2.5.1
       env: CHECK=license_finder
       bundler_args: ""
 
@@ -56,6 +56,10 @@ matrix:
       env: PUPPET_GEM_VERSION='https://github.com/puppetlabs/puppet.git#master'
     - rvm: 2.5.1
       env: PUPPET_GEM_VERSION='https://github.com/puppetlabs/puppet.git#6.0.x'
+    - rvm: 2.4.3
+      env: PUPPET_GEM_VERSION='https://github.com/puppetlabs/puppet.git#5.5.x'
+    - rvm: 2.1.9
+      env: PUPPET_GEM_VERSION='https://github.com/puppetlabs/puppet.git#4.10.x'
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