To use gem install insteaad of bundle install

Author: hsbt

appveyor.yml

@@ -2,8 +2,7 @@
 clone_depth: 10
 install:
   - SET PATH=C:\Ruby%ruby_version%\bin;%PATH%
-  - gem install bundler --no-document -f
-  - bundle install
+  - gem install minitest
 build: off
 test_script:
   - ruby -Ilib exe/rake