Added option for Gulp logging

Typically Gulp plugins suppress the output of the native module and add an option to log the output. Basically:

```js
.pipe(bless({
  log: true
}));
```

Gives the option of keeping the command line clean.
`!0` and `!null` *are* `=== true`. Sure `1` isn't `=== true` but why restrict it? Let's allow them to pass any "truthy" value to turn on logging.