Add offline test mode / config flag
run swagger specs test before server restart
Systematically catch and log uncaught exceptions
Limit the number of incoming connections per worker

We want to produce some back-pressure in case back-end systems are slow to
avoid being swamped by requests & using a lot of memory. 500 concurrent
connections per worker should be a good starting point.

Also remove the backlog setting from the listen call. somaxconn is really more
important for round-robin distribution & thus bounding of latency in high-load
situations.
Merge pull request #77 from hardikj/offline

Add offline test mode / config flag
Merge pull request #85 from gwicke/master

More logging and robustness improvements
Add tests and partial implementation for no-cache handling