Pyramid-basemodel

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Default `basemodel.should_create_all` to `False`. This will break apps that rely on tables being created by default. However, it's much saner to only
invoke both `metadata.create_all(engine)` and `metadata.drop_all(engine)` when
explicitly told to, particularly as most applications will use migrations
to manage the database schema.

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Faff about horribly with the slug generation code.

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Fix Python3 `KeyError` syntax bug.

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Support dotted path `sqlalchemy.pool_class` configuration.

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Provide `util.get_object_id` function and stamp
`sqlalchemy.ext.declarative.declarative_base()` subclasses with the
`interfaces.IDeclarativeBase` interface.

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Fix Python3 support (requires 3.3 for the unicode literal character).