CVE-2013-1775 osx sudo password bypass post module

[Link to cvedetails.com](http://www.cvedetails.com/cve/CVE-2013-1775/)

### verification
- [ ] in System Preferences, create a new user with no admin privileges. log in as the new user.
- [ ] gain a session on the new user, run the post module and verify that it fails with "user not in admin group"
- [ ] log back into an admin account. grant the new user admin privs in System Preferences. you will have to restart your computer (and end your session).
- [ ] log in again as the new user. gain another session on the new user.
- [ ] run the post module and verify that it fails with "user has never run sudo".
- [ ] on the new user's account, run `sudo whoami`, and put in your password
- [ ] log out (your session will die) and back in again. re-open your session.
- [ ] run the post module again, verify that it succeeds (`/usr/bin/whoami` should print 'root')