ids function

Instead of doing this:

```js
var companyPendingIds = await db('companyupdate').find(
    { status: 'pending' },
    { fields: { id: 1 } }
  )
  companyPendingIds = companyPendingIds.map((x) => x.id)
```

We'd like to do this:

```js
var companyPendingIds = await db('companyupdate').ids({ status: 'pending' })
```
