Feature request: pg schemas

It seems as though there might be an issue with using squid + postguard when using postgres schemas, I would assume that when referencing tables in schemas one should use the FQN of the table in the `defineTable` method but this does not seem to work as intended with postguard.

I would expect the following to work and type check correctly, in addition it seems as postguard ignores the schema portion of table names when it checks a query

```
defineTable('schemaName.tableName`, {...})
```