Fixes for RSpec tests on Windows

* Skip Berkshelf::API actions on Windows
* Use && instead of ; in command line operations
* Skip tests using Berkshelf::API::RSpec.berks_dependency
* Rewrite checks using temporary directories
* Use double quotes when shelling out
* Remove stderr redirects to /dev/null
* Git on Windows does not create full path to tmpdir, do this in clone
* Ensure that there is a / in the Mercurial URI
* Work around Thor::Shell::Basic behaviour differences on Windows