Chef should always print stderr and stdout when a shelled-out command fails

chef only shows full output for failed shell commands when logging is set to debug. requiring users to run the command again with -l debug is a hassle, and makes it much more difficult to catch intermittent errors.

One way to do this is to package the response from output_of_command into an object with the exit status, stdout and stderr. then if the exit status is not correct, it can be made to error.