Allow changing pg.defaults

[swissspidy]

In #51 I noted how it's not possible to change pg.defaults via Massive. node-postgres allows overriding a few defaults. Here's an example:

var pg = require('pg');
pg.defaults.poolSize = 25;

//pool is created on first call to pg.connect
pg.connect(function(err, client, done) {
  done();
});

pg.defaults.poolSize = 2;
//pool still has a size of 25
pg.connect(function(err, client, done) {
  done();
});

//creating a new pool by using a different connection string
//will create this second pool with a size of 2
pg.connect('other-pool', function(err, client, done) {

});

The runner class (DB.prototype.query and DB.prototype.stream, specifically) could be extended to allow changing these defaults.

[robconery]

I think @dmfay we could accommodate this on startup - maybe tacking on pgDefaults option or something in the connection? Changing the poolsize is particularly interesting although the date issue referenced in #51 will cause more issues but... whatever :).

Thoughts? @xivSolutions?

[xivSolutions]

Agree about adding a pgDefaults _option _on start-up. There are a number of reasons that would be handy, including (for those who choose to go this route) setting the option parseInputDatesAsUTC mentioned by the OP in #51.

Pool size management is the big win here I think. As far as the date stuff, to me that's just JS quirkiness, and Massive already does the correct thing by staying out of the way and allowing the irritating, but "normal" JS behavior to remain.

[dmfay]

It'd be pretty great to be able to turn on parseInt8 and get counts back as proper numbers too! Definitely agree with John that it needs to be something the user has to explicitly enable themselves though.