Incorrect attributes in generated `meta` tags

[apjanke]

In the HTML output, there are a couple meta tags being generated by Ronn.

  <meta http-equiv='content-type' value='text/html;charset=utf8'>
  <meta name='generator' value='Ronn/v0.7.3 (http://github.com/rtomayko/ronn/tree/0.7.3)'>

I think these are invalid. The meta element doesn't take a name attribute; it takes a content attribute instead. These should be:

  <meta http-equiv='content-type' content='text/html;charset=utf8'>
  <meta name='generator' content='Ronn/v0.7.3 (http://github.com/rtomayko/ronn/tree/0.7.3)'>

[apjanke]

Superset of #81.

[apjanke]

Fixed in my Ronn-NG fork at apjanke/ronn-ng@d645829.