Replace react-markdown with markdown-it

[mattkrick]

react-markdown isn't gonna be powerful enough for what we want because we need to create new nodes based off of new tokens such as #, @, :.
remarkjs/react-markdown#61

What we want is https://yarnpkg.com/en/packages?q=markdown-it
(PS look how awesome yarn makes it to find the most popular packages! npm can just go pound sand.

There isn't a popular react wrapper for it, but i'm assuming that's because all you have to do is
<span dangerouslySetInnerHTML={{__html: this.renderMarkdown(this.props.source)}}/>.

[ackernaut]

🔥