4.2.0

• deprecate app.del() -- use app.delete() instead
• deprecate res.json(obj, status) -- use res.json(status, obj) instead
  • the edge-case res.json(status, num) requires res.status(status).json(num)
• deprecate res.jsonp(obj, status) -- use res.jsonp(status, obj) instead
  • the edge-case res.jsonp(status, num) requires res.status(status).jsonp(num)
• fix req.next when inside router instance
• include ETag header in HEAD requests
• keep previous Content-Type for res.jsonp
• support PURGE method
  • add app.purge
  • add router.purge
  • include PURGE in app.all
• update debug to 0.8.0
  • add enable() method
  • change from stderr to stdout
• update methods to 1.0.0
  • add PURGE