appveyor.yml in chandler-0.7.0 vs appveyor.yml in chandler-0.8.0

@@ -2,15 +2,16 @@
 
 skip_tags: true
 
 environment:
   matrix:
-    - ruby_version: "21"
-    - ruby_version: "21-x64"
+    - ruby_version: "25"
+    - ruby_version: "25-x64"
 
 install:
   - SET PATH=C:\Ruby%ruby_version%\bin;%PATH%
-  - gem install bundler --no-document -v 1.10.4
+  - gem update --system
+  - gem install bundler --no-document
   - bundle install --retry=3
 
 test_script:
   - bundle exec rake