Fix "shared folder guest path is used multiple times" error message when multiple chef provisioners are used.

Fix "shared folder guest path is used multiple times" error message when
multiple chef provisioners are used on a VM.  This issue affects both
linux and windows guests simply by having the vagrant-windows plugin
installed.  Also, prevent the vagrant-windows plugin from affecting the
shared folder name of linux guests.
Fixed line endings on share_folders.rb to make them consistent with the other rb files in this project
Merge pull request #68 from keiths-osc/shared_folder_fix

Fix for vagrant-windows issue #67