Add batch cleanup code for windows

This will rebuild the batch files to use the relative path to the embedded ruby. Consequently, this will solve https://github.com/opscode/chef-dk/issues/221, however I have no idea why it is using bin\ruby.exe instead embedded\bin\ruby.exe

This change is tested by https://github.com/opscode/chef-dk/pull/235
 
cc @btm @sersut @opscode/client-engineers 
Should this be using string comparison?  I've had bad experiences with that before