Refactor shell_init to allow for exports in different types of shells
Added .ruby-version to gitignore
Added powershell to chef shell-init
Added powershell to supported shell in spec
Posh is powershell in chef shell-init
Refactor shell_init_spec
Added specs for shell-init powershell
Merge pull request #253 from opscode/jdmundrawala/powershell

Adding powershell to chef shell-init