add comment to Unified Diff Formatter making it clear the output is unsafe for use in HTML as is
FS#2738, fix double encoding of html entities in RSS feeds (updates feed.php for changes to Diff class introduced in PR#179)
FS#2748, fix double encoding of html entities in subscription email diffs (updates subscription.php for changes to Diff class introduced in PR#179)
Merge pull request #211 from splitbrain/nonwikidiffs

Fix double encoding of html diff output in syndicated feeds and subscrition emails