wth 'ut8' charset. should be `utf-8`

my library can't decode `ut8` charset

    # in private IRC channel
    <keedi> hshong: http://preludels.com/ 혹시 이것도 쓰세요?
    <misskim> [Unknown encoding 'ut8' at lib/Hubot/Scripts/shorten.pm line 77.
Merge pull request #62 from aanoaa/gh-pages-typo

wth 'ut8' charset. should be `utf-8`