Sometimes options page MD preview doesn't initially render

[adam-p]

This error results:

Error: TypeError: rawMarkdownIframe is undefined
Source File: resource://markdown_here_common/options.js
Line: 246

What's happening is that the preview iframe is loading before the DOM of the options page, so the options-iframe-loaded handler fires, but renderMarkdown() isn't yet ready.

Going to fix by making sure the options page is also loaded.

[adam-p]

Fixed in rev 3c9ed94