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