(maint) update travis to not use bundle update --system

.travis.yml

@@ -5,7 +5,9 @@ cache: bundler
 before_install:
   - bundle -v
   - rm -f Gemfile.lock
-  - gem update --system $RUBYGEMS_VERSION
+  - "# Update system gems if requested. This is useful to temporarily workaround troubles in the test runner"
+  - "# See https://github.com/puppetlabs/pdk-templates/commit/705154d5c437796b821691b707156e1b056d244f for an example of how this was used"
+  - '[ -z "$RUBYGEMS_VERSION" ] || gem update --system $RUBYGEMS_VERSION'
   - gem --version
   - bundle -v
 script:

metadata.json

@@ -81,6 +81,6 @@
     }
   ],
   "template-url": "https://github.com/puppetlabs/pdk-templates#master",
-  "template-ref": "heads/master-0-g643529a",
-  "pdk-version": "1.14.1"
+  "template-ref": "heads/master-0-gcaed9d7",
+  "pdk-version": "1.15.0"
 }