Add schema.org/Person metadata to theme boilerplate

Hi there,

I'm starting to develop my own theme and I thought it'd be nice to encourage developers to implement http://schema.org/ metadata in themes to make it available for resumes.

I made two separate commits:

- the first one keeps the markup same as before, I only added microdata attributes. Here's an example of the kind of data that's in: https://www.google.com/webmasters/tools/richsnippets?q=uploaded:80050af6c91c6b8874aaa2661b3a8eb7

- the secund commit goes further and adds a few `<span>`s to properly tag the person's address, email, website and telephone. Example with those: https://www.google.com/webmasters/tools/richsnippets?q=uploaded:80050af6f39c9714cb850789c45543a9 (notice how the Google Search excerpt is enriched with "San Francisco California - ‎Programmer"!).

Do tell me if this PR should include only the first commit.

BTW the following things could also be added, but will potentially require some more markup:

- Relationship between person and company/volunteer items
- Publications
- References