Cleanup processing and security & privacy

[igrigorik]

This should, I believe, address the discussions in:

• https://github.com/w3c/beacon/issues/10
• https://github.com/w3c/beacon/issues/15
• https://github.com/w3c/beacon/issues/16

Preview: https://rawgit.com/w3c/beacon/cleanup/index.html

[igrigorik]

@annevk thanks, should be fixed now.

[toddreifsteck]

LGTM