This feature is to add pre-post hook to run before posting the request. This patch demonstrate how we can do format checking before posting the review so that we can make edit locally to fix formatting issues locally. The user can use --no-pre-post-hook to turn off the hook if neccessary.

Test with "pyflakes . && nosetests" command specified in rbtools/.reviewboardrc and check if the command is run.

Check if the pre-post-hook is turned off if the --no-pre-post-hook flag is on.