response.body may be nil

we can get back things like http 204 with no response body and calling
chomp on that throws a bad stack track.  this sends nil back with
the response and the caller can determine how to handle the 204.
Remove the bootstrap templates that does chef install via gems.
Deprecate --distro and --template-file options in favor of --template.
Remove encrypted_data_bag_secret distribution via Chef::Config and enable distributing it via knife[:secret] and knife[:secret_file].
Fixes based on the PR comments.
Specs for bootstrap cleanup.
Fixes based on PR comments.
Update CHANGELOG and RELEASE_NOTES with bootstrap changes.
Merge pull request #1885 from opscode/sersut/bootstrap-12

Chef 12 bootstrap cleanup
Merge pull request #1896 from opscode/lcg/1869

response.body may be nil