SetWrapper.create() bug fixed
Enable foreign key support in SQLite
Renaming TableNotExists -> TableDoesNotExist
Add pony.thirdparty package into the distributive
Update version to 0.4.9
Pony ORM release 0.4.9:
1. Database create_tables()/drop_all_tables() methods
2. Database.drop_table(name), Entity.drop_table(), Set.drop_table() methods
3. Database.disconnect() methods (allows SQLite files deletion after disconnection)
4. Pony now automatically enables foreign key checks in SQLite
5. Entity.exists(...) method added
6. distinct() function added: select((s.group, sum(distinct(s.gpa))) for s in Student)
7. Refactoring & bugfixes

Conflicts:
	setup.py