* Add dependency on idn-ruby to speed up URI normalization
* Use normalized_host instead of normalize.host when applicable
When we are only interested in the normalized host, calling normalized_host
avoids normalizing the other components of the URI as well as creating a
new object
* Fix nil input not handled well in AuthorExtractor concern
* Fix hard error in ProcessFeedService when replied-to status has been deleted
* Fix nil errors in ProcessInteractionService when favourited status
cannot be found
Fix#2196 - Respond with 201 when Salmon accepted, 400 when unverified
Fix#2629 - Correctly handle confirm_domain? for local accounts
Unify rules for extracting author acct from XML, prefer <email>, fall back
to <name> + <uri> (see also #2017, #2172)
