Merge pull request #1682 from MSP-Greg/update-travis-ruby

update travis rubies - 2.3.8, 2.4.5, 2.5.3

.travis.yml

@@ -3,16 +3,21 @@ sudo: false
 group: beta
 language: ruby
 cache: bundler
+
 before_install:
-  # https://github.com/travis-ci/travis-ci/issues/9383#issuecomment-377680108
-  # recent versions of RubyGems include bundler
-  - gem update --system
+  # rubygems 2.7.8 and greater include bundler
+  - |
+    rv="$(ruby -e 'STDOUT.write RUBY_VERSION')";
+    if   [ "$rv" \< "2.3" ]; then gem update --system 2.7.8 --no-document
+    elif [ "$rv" \< "2.6" ]; then gem update --system --no-document --conservative
+    fi
+  - ruby -v && gem --version && bundle version
 
 rvm:
   - 2.2.10
-  - 2.3.7
-  - 2.4.4
-  - 2.5.1
+  - 2.3.8
+  - 2.4.5
+  - 2.5.3
   - ruby-head
   - jruby-9.2.0.0
 
@@ -21,9 +26,9 @@ matrix:
   include:
     - rvm: ruby-head
       env: RUBYOPT="--jit"
-    - rvm: 2.3.7
+    - rvm: 2.3.8
       os: osx
-    - rvm: 2.5
+    - rvm: 2.5.3
       os: osx
     - rvm: jruby-head
     - rvm: rbx-3