.travis.yml in review-3.0.0 vs .travis.yml in review-3.1.0

@@ -9,19 +9,27 @@
       - texlive-latex-extra
       - texlive-latex-recommended
       - dvipng
 
 before_install:
-  - gem update --system
-  - gem update bundler
+  - |-
+    RUBY_VER=`ruby -e "print RUBY_VERSION"`
+    if [ "$RUBY_VER" = "2.1.10" ]; then
+      gem install bundler -v '< 2'
+    elif [ "$RUBY_VER" = "2.2.10" ]; then
+      gem install bundler -v '< 2'
+    else
+      gem update --system
+      gem install bundler
+    fi
 
 rvm:
-##  - 2.0
   - 2.1
-  - 2.2.7
-  - 2.3.4
-  - 2.4.1
-  - 2.5.0
+  - 2.2.10
+  - 2.3.8
+  - 2.4.5
+  - 2.5.3
+  - 2.6.0
 ##  - ruby-head
 
 branches:
   only:
     - master