Render notes without a wrapped <p> tag as textile for backwards compatibility

We use Redmine at work, and I would love to implement the ckeditor, but there are already a lot of notes that are present in the textile format. Rather than have these look weird when the ckeditor is implemented, I would rather have the old notes properly formatted as well as new html formatted notes.

So this pull request does a check when rendering the note to look for any notes not wrapped in a <p> tag and uses the default textile formatter on those. This keeps old notes as they were and also properly renders new notes.