Better logs, better inserts

• auth mechanisms are now implemented in aiosmtpd
  (thanks Arzaroth for PR)
• huge improvements to handling DB inserts. Now all messages are stored in an internal queue,
  then it's saved to the DB. It solves many problems with performance and single-threaded
  SQLite (thanks KathrynN for reporting)
• fixed API response when there is no data to return (#3) (
  thanks KathrynN for reporting)
• improved logging system, now log messages has log levels, also many simplifications in
  logging system
• Sendria now introduce as itself when connect through SMTP (also --smtp-ident CLI param added)
• minor fixes and performance issues solved, updated dependencies
• next step in cleanups and making code modern

The new beginning

• complete rewrite of backend part. MailTrap is using asyncio and aio-libs now:
  • switch to aiohttp from Flask
  • switch to aiosmtpd from smtpd
  • switch to aiosqlite from sqlite3
  • changed logger to structlog
• using asynchronous version of libraries drastically improved performance
• MailTrap now can send a webhook about every received message
• show in GUI information about envelope sender and recipients
• all API requests has their own namespace now: /api
• allow to replace name of application or url in template
• block truncating all messages from GUI (on demand)
• fixed issues with WebSockets, should refresh mails list and reconnect if disconnected
• fixed issues with autobuilding assets
• many cleanups and reformatting code
• addons for nginx and supervisor