Replace window.badgeData bootstrapped array w/ data attributes.

This does two things:

(1) Gets rid of an XSS vulnerability in the backpack by forcing
    the serialized badge data to be escaped.
(2) Removes the need for an inline script tag, which brings us one
    step closer to supporting Content Security Policy as per the
    practices mentioned here:

      https://github.com/blog/1477-content-security-policy
converted JSON.parse(.attr()) to .data(). Thanks arhayward.
Merge pull request #857 from toolness/window-badgedata-removal

Replace window.badgeData bootstrapped array w/ data attributes.