Fix HTML tags in topic titles (PR #2277)

We no longer sanitize titles before saving to the database since it would cause problems like HTML entities showing up when you try to edit a topic title. It was never really necessary since we only render fancy_title directly and never title. (title is rendered in the SEO-friendly views, but Rails takes care of the escaping in those cases.)

The escaping logic used here is the same that is used both in lodash and onebox. See:



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