* 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
Setting PostgreSQL 9.5 as the main version to test against.
NOTE: The following settings are required for 9.5 to work:
```
sudo: required
dist: trusty
```
A long standing bug was the pure JS client didn't accept or call a callback on `client.end`. This is inconsistent with both the documentation & general node patterns.
This fixes the issue & adds a test. The issue did not exist in the native version of the client.
* 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
The promise adapter I had implemented wasn't spec compliant: it didn't accept both `onSuccess` and `onFailure` in the call to `query#then`. This subtly broke yield & async/await because they both rely on `onError` being passed into `Promise#then`. The pool was also not returning the promise after a client was acquired, which broke awaiting on `pool.connect` - this is also fixed now.
