Merge pull request #30 from mikewest/mixed

MIX: Adding a draft mixed content spec.
Snapshotting the initial draft.
Fix some minor typos
Merge pull request #31 from mathiasbynens/patch-1

Fix some minor typos
MIX: Whitespace.
MIX: More typos.
MIX: exports.
MIX: Clarify 'file:', add UNC issue.
MIX: Updating fetch algorithms to take requests and responses.
MIX: s/document/JavaScript global environment/g
MIX: Version history.
MIX: Check all ancestor contexts, rather than just the top-level.
MIX: Simplify version history link.
[REFERRER]: Getting started.
[REFERRER]: Moar.
[MIX]: 'Set request's referrer.' algorithm.
[REFERRER]: Using 'referrer source'.