Merge pull request #12 from jeremybanks/master

Raise an error for invalid SE OpenID logins (includes live tests)
Prevents username and password from being exposed in error tracebacks.

This is only safe as long as the username and password are never stored
in any new variables, but are only passed directly as

    browser.loginSEOpenID(live_testing.username, live_testing.password)

This change includes a test change because that test was leaking the
password's actual length.