Create appveyor.yml to run on windows CI service

Add Appveyor configuration file so this can be built on the Appveyor CI service (windows).

This basically runs the same script as Travis-CI does using test_all.sh.

Appveyor comes with x86 version of Ruby installed with Rake and Bundler see also: http://help.appveyor.com/discussions/problems/691-ruby-gem-install-bundler-hanging