MIME type parsing, single quote parameter values

[annevk]

This appears to be a Chrome-only feature for which I filed https://bugs.chromium.org/p/chromium/issues/detail?id=772350.

HTTP/1.1 200
Content-Length: 55
Content-Type: text/html;charset='gbk'

<script>document.write(document.characterSet)</script>

Filed here to ensure the test suite covers it.

[annevk]

Bug filed (and already fixed!) and tested by #42, so closing.