Correcting the final set of unit tests.

This commit addresses the final 6 failing unit tests for sails-postgresql.
The changes are only to the tests, and represent changes to the expected
results instead of corrections of aberrant behavior.

groupBy tests:
These tests were corrected by adding an aggregation (avg, in this case)
to the input. The matching output query now matches
```
SELECT "test"."name",
       CAST( AVG("test"."age") AS float) AS age
FROM "test" AS "test"
WHERE LOWER("test"."name") = $1
GROUP BY "test"."name"
```

skip tests:
The LIMIT 184467440737095516 clause was added to support MySQL syntax,
but it doesn't seem to cause problems for Postgres, so I added the
limit clause to the expected output. If this isn't satisfactory, we
could make the LIMIT clause inclusion based on a new SqlOption value.

where tests:
Corrected spacing in the output query. The actual fix for these tests
were in balderdashy/waterline-sequel#18.

join tests:
I don't love the solution to this one. The query was changed from:
```
SELECT
	user.name,
	user.id,
	user.createdAt,
	user.updatedAt,
	pets_pet.name AS pets_pet__name,
	pets_pet.id AS pets_pet__id,
	pets_pet.createdAt AS pets_pet__createdAt,
	pets_pet.updatedAt AS pets_pet__updatedAt,
 	pets_pet.owner AS pets_pet__owner
FROM user
LEFT JOIN pet AS pets_pet
ON user.id = pets_pet.owner
WHERE user.id IN (
			SELECT user.id
			FROM user
			LIMIT 30
			OFFSET 0)
```
to
```
SELECT
	user.name,
	user.id,
	user.createdAt,
	user.updatedAt,
	__pet.name AS id___name,
	__pet.id AS id___id,
	__pet.createdAt AS id___createdAt,
	__pet.updatedAt AS id___updatedAt,
	__pet.owner_id AS id___owner_id
FROM user AS user
LEFT OUTER JOIN pet AS __pet
ON user.id = __pet.owner
LIMIT 30 OFFSET 0
```
these are functionally the same, but the inputs needed to change drastically
to generate them.