Added basic microdata

Generally looks good, but itemprop="author name" would be technically invalid. From [W3C](http://www.w3.org/TR/microdata/#names%3a-the-itemprop-attribute):

> The itemprop attribute, if specified, must have a value that is an unordered set of unique space-separated tokens that are case-sensitive, representing the names of the name-value pairs that it adds. The attribute's value must have at least one token.

This means you are defining two `name` values for the scope `BlogPosting`. I think your intent was to specify that `span` was the post's `author` and a `Person` whose name is the contents, correct? If you wanted to do that, you'd probably need to nest spans.

Instead, I'd follow the lead of schema.org's [Article](http://schema.org/Article) examples (which is the parent of BlogPosting):

```html
<div itemscope itemtype="http://schema.org/Article">
  <span itemprop="name">How to Tie a Reef Knot</span>
  by <span itemprop="author">John Doe</span>
  This article has been tweeted 1203 times and contains 78 user comments.
  <meta itemprop="interactionCount" content="UserTweets:1203"/>
  <meta itemprop="interactionCount" content="UserComments:78"/>
</div>
```