Fix encoding issues

`SimpleRSS#unescape` blindly forced binary encoding on all the string values causing encoding issues (such as https://github.com/cardmagic/simple-rss/issues/15) in code using `simple-rss`. Just remove all the fiddling with encodings. I can't figure out any reason why there would be any need for that.

For some odd reason gemspec wasn't up to date with published gem version. Dunno why's that. Updated it too.