.travis.yml - fix RubyGems update code

Author: MSP-Greg

.travis.yml

@@ -1,8 +1,14 @@
 language: ruby
 cache: bundler
 before_install:
-  - gem update --system 2.7.7
-  - gem install bundler -v 1.16.2
+  # rubygems 2.7.8 and greater include bundler
+  - |
+    rv="$(ruby -e 'STDOUT.write RUBY_VERSION')";
+    if   [ "$rv" \< "2.3" ]; then gem update --system 2.7.10 --no-document
+    elif [ "$rv" \< "2.7" ]; then gem update --system --no-document --conservative
+    fi
+  - ruby -v && gem --version && bundle version
+
 addons:
   apt:
     packages: