update .travis.yml

Author: Fivell

.travis.yml

@@ -4,20 +4,14 @@ env:
     - RAILS=4.2.6
     - RAILS=5.0.0
 rvm:
-  - 1.9.3
-  - 2.0.0
   - 2.1.9
   - 2.2.5
   - 2.3.1
 matrix:
   exclude:
-    - rvm: 1.9.3
-      env: RAILS=5.0.0
-    - rvm: 2.0.0
-      env: RAILS=5.0.0
     - rvm: 2.1.9
-      env: RAILS=5.0.0
+      env: RAILS=5.0.0 # Rails 5.0 requires Ruby 2.2.2 or newer
 before_install:
-  - gem install bundler -v '= 1.9.3'
-  - gem update --system
-  - gem --version
+  - gem update --system # use the very latest Rubygems
+  - rvm @global do gem uninstall bundler -a -x
+  - rvm @global do gem install bundler -v 1.14.6 # latest version known to work