Adding "pass" to the list of terms to scrub.

This is sent by Drupal's login page- and I can imagine is used by many other frameworks/CMSes, too.

Ps. I don't know if I'm okay to do any pull requests on this project, but I thought it was quite a bit of a security issue.
Merge pull request #14 from MaffooBristol/patch-1

Adding "pass" to the list of terms to scrub.