FIX: force encoding for title field

Job exception: incompatible character encodings: UTF-8 and ASCII-8BIT
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This exception rise up for correct(!) UTF-8 cyrillic (in my case, but non-latin overall, I suppose) in title field during RSS polling (feed polling url) and breaks topics creation.
So, just force_encoding() makes it work.
due to travis error message: can't modify frozen string
Merge pull request #2851 from VickMellon/title_encoding_cast

FIX: force encoding for title field