title: sequel never returns utf-8, just ascii-8bit
body: <p>There is this mysql database I'm trying to connect to. DataMapper fetches everything nicely in UTF-8 but Sequel always returns strings in ASCII-8bit which produces errors with .to_json.</p>
  
  <p>I have tried several things in order to get it to work.</p>
  
  <pre><code>Encoding.default_external = Encoding::UTF_8  
  Encoding.default_internal = Encoding::UTF_8  
  DB.run 'set names utf8'  
  Sequel.mysql 'db', (...), :encoding =&gt; 'utf-8'  
  </code></pre>
  
  <p>I have gems: mysql (2.9.0) (tried without), mysql2 (0.3.11) and sequel (3.42.0)</p>
  
  <p>The only thing that works is manually forcing the encoding on every string which is MUCH less than ideal.</p>