add spec to demo blanking props
Discourse as a Mailing List improvements

FEATURE: context is not emailed if we previously emailed you the post
FEATURE: site setting to enable_watch_new_topics , false by default.
  When enables users can elect to watch everything by default
FIX: Custom email subjects (x quoted you in [title], x replied to [title])
  was removed, this broke email grouping. TBD, include info in footer somehow
FIX: topic user specs were messy, reduce side effects
remove "host" so it uses sockets by default, easier to configure
FEATURE: backport a minimal String#scrub
BUGFIX: invalid byte sequence in email would explode all processing
BUGFIX: invalid referer would cause 500 errors