markdownToHTML should return a non-optional string

[Ole Begemann]

public func markdownToHTML(markdown: String) -> String? {
    let outString = cmark_markdown_to_html(markdown, markdown.utf8.count, 0)
    return String(UTF8String: outString)
}

I think this function should return a String instead. If you think about it, any text is valid Markdown, so the conversion can't really fail (or at least it shouldn't). The implementation currently returns nil if String(UTF8String: outString) fails, but this should never happen, either. We know cmark_markdown_to_html returns a valid null-terminated UTF-8 string, after all.

[Ole Begemann]

The same goes for the html, xml, commonMark, and latex properties on Node.

[Chris Eidhof]

You are right!