2.0.0

• Change default cookie name to session
• Change .populated to .isPopulated
• Create new session for all types of invalid sessions
• Drop support for Node.js 0.8
• Remove private req.session.save()
• Remove the key option; use name instead
• Remove undocumented req.session.length to free up key name
• Remove undocumented req.sessionCookies and req.sessionKey
• Save all enumerable properties on req.session
  • Including _-prefixed properties
• Use Object.defineProperty instead of deprecated __define*__
• Use safe-buffer for improved Buffer API
• deps: cookies@0.8.0
  • Fix check for default secure option behavior
  • Fix maxAge option preventing cookie deletion
  • Support "none" in sameSite option
  • deps: depd@~2.0.0
  • deps: keygrip@~1.1.0
  • perf: remove argument reassignment
• deps: debug@3.2.7
  • Add DEBUG_HIDE_DATE
  • Add 256 color mode support
  • Enable / disable namespaces dynamically
  • Make millisecond timer namespace-specific
  • Remove DEBUG_FD support
  • Use Date#toISOString() when output is not a TTY
• deps: on-headers@~1.0.2
  • Fix res.writeHead patch missing return value
• deps: safe-buffer@5.2.1
• perf: reduce the scope of try-catch deopt
• perf: remove internal reference to request from session object