Changed test_emails to use selenium.

[chris-leach]

This fixes an issue that was causing password reset tests to pass when run alone, but fail when the whole test suite was run.

[mikebryant]

Why doesn't the normal test client work for this?
Selenium shouldn't be required to test a simple view...

[chris-leach]

I'm still unsure. The email backend seems to fail completely silently, and I've been unable to find anyone else with the same issue, but

1. this is definitely the test that causes the others to fail.
2. this is the only test in the suite that currently uses the default client - all the rest use selenium.

[mikebryant]

I believe this is superseded by #192