This improves the test capabilities a bit by taking some useful

functions from EvolutionTestCase (assertSQLMappingEqual(),

get_sql_mapping(), and related attriubtes) into TestCase, so that

more unit tests can have access to them.
New utility and assertion functions have been added for unit tests to

use. These include:


record_evolutions(): Records new Evolution entries in the

  database.


record_applied_migrations(): Records new applied migrations in the

  database.


assertEvolutionsEqual(): Asserts that a list of Evolution entries

  match expectations.


assertAppliedEvolutions(): Asserts that a list of applied

Evolution entries match expectations.


assertAppliedMigrations(): Asserts that a list of applied migrations

   match expectations.


And finally, upon teardown of a unit test, the built-in test apps are

now deleted from the database and unregistered from Django.

Unit tests pass on all versions of Python.