* When connection fail, emit the error.
If client connect failed, emit the connection error rather than swallowing it.
* Add test for connection error.
* Pool.query calls cb if connect() fails
Old behavior was that if connect called back with an error, the promise would get rejected but the cb function would never get called.
* Test that Pool.query passes connection errors to callback
* Fixes to standardjs compliance
* fail: "connect" event only on success
Double callback invocation will also cause this to fail.
* avoid double callback: _create
If `client.connect` returns an error, then the callback for `Pool#_create` is only invoked once. Also the `connect` event is only emitted on a successful connection, the client is otherwise rather useless.
* legacy compat; don't use Object.assign
* legacy compat; events.EventEmitter
* Support function-like construction
Remove the necessity of using `new` in front of the `Pool`, i.e. allow it to be used as a regular function. This is following https://github.com/brianc/node-postgres/issues/1077
* add Pool factory test
