Use quoting rather than shellescape to give Windows compatibility

Ran into a similar error as #128, but on Windows.

Ridley::Errors::CookbookSyntaxError: Invalid ruby files in cookbook: windows (1.10.1).
C:/opscode/chef/embedded/lib/ruby/gems/1.9.1/gems/ridley-1.2.5/lib/ridley/chef/cookbook.rb:175:in `validate'

I'm doing a berks upload with no paths specified, but my home directory has a space in the name.

Turned out that shellescape does the wrong thing with Windows paths, as to quote the [Shellwords manual page](http://www.ruby-doc.org/stdlib-1.9.3/libdoc/shellwords/rdoc/Shellwords.html), "This module manipulates strings according to the word parsing rules of the UNIX Bourne shell". Instead, if we put quotes around the paths, then everything (or at least spaces) should work on both Windows and Unix platforms.