Stop adding to 00_utils!!

For the foreseeable future, we want to discontinue use of 00_utils.rake, in
favor of testable classes in lib/packaging/util. This commit adds a warning to
stop adding to 00_utils.rake for anything.

Signed-off-by: Moses Mendoza <moses@puppetlabs.com>
Merge pull request #269 from MosesMendoza/maint/master/stop_00_utils

Stop adding to 00_utils!!