Lazy-record

Fixed a bug where pre-made validations were not working correctly. Now, you can (successfully) do

python
class MyModel(lazy_record.Base):
__validates__ = {"my_attr": unique}

Enhanced querying by adding the following methods to Query objects:
- select (SQL `SELECT`)
- group (SQL `GROUP BY`)
- having (SQL `HAVING`)

Using `where` with a list or tuple argument now generates a query using `IN`

python
Cantaloupe.where(ripeness=[1, 2, 3])


SQL
SELECT cantaloupes.* FROM cantaloupes WHERE cantaloupes.ripeness IN (1, 2, 3)


`len` now works on Query objects, and generates a `SELECT COUNT` in SQL for fast counting.

Added support for multi-level joins.

Now has full test coverage and is fully documented.

This is an early development release of lazy_record. Primarily intended for users of the greenhouse application.