update gems
cleanup and update Berksfile
cleanup and unify file comment headers
remove constants:

* there were many warnings about constants being
  reassigned, and these are not being used in any
  other context, so they have been converted to 
  local variables
clean up recipe, guided by tests
add `chefspec` coverage
run `chefspec` on travis ci
Merge pull request #150 from phlipper/chefspec

add `chefspec` coverage