default parameter collides with overload

- 2nd constructor is `package this(string url)`
Always check exit flag while processing yield()ed tasks. Fixes #720.
Don't query the clock and update the libevent timer event when no timers are pending.

See #721.
add .editorconfig for vibe-d

- tabwidth = 4 spaces
Add ip-based client certificate authentication to https servers
typed enum for MongoConnection.defaultPort
fix Issue 719 - runWorkerTask does not support implicit conversion of arguments

- Deduce deduce function type and argument types
  separatly to support implicit convesions.

- Pass arguments by ref when possible
Added description for Json error handling