OC-10380: skip checksumming for no-content files
OC-10380: add polymorphism
spec tests for checksum

- plus stubbing of things that weren't stubed
- and changing stub! to stub
fix windows pathing issue in spec tests
[CHEF-4110] Add whyrun_safe_ruby_block resource
Merge pull request #743 from jaymzh/CHEF-4110

 	[CHEF-4110] Add whyrun_safe_ruby_block resource
Merge pull request #1111 from opscode/lcg/OC-10380

OC-10380: skip checksumming for no-content files