* FIX: Properly convert quotes to Markdown
When quoting a quote it used to convert the quote header, including the
user avatar and username, into a image and some text and then the
contents. This also caused issues when quoting full paragraphs (or when
selecting paragraphs by triple-clicking) because the user avatar and
name from the following quote would also be included.
This commit implements the support necessary to convert
<aside class="quote"> elements to proper Discourse quotes.