Replace f.error_messages in nifty auth view templates

Update the nifty authentication view templates to explicitly print out validation errors since the error_messages method in ActionView::Helpers::FormBuilder was deprecated in Rails 3

I ran rake but there were a couple of uninitialized constant errors around bcrypt. I couldn't figure out how to circumvent these errors, but given that I only made changes to view templates, I think the errors were unrelated.