c99f5c4ec1
All connection-related functions are now in connection.py. Created a ConnectionManager class for interacting with a collection in the database. Top-level document classes have an instance of a ConnectionManager (Document.collection). Defined a 'save' method on top-level document's that uses the collection manager's '_save_document' method to save the document to the database. Added tests for CollectionManagers -- all unit tests now require a valid connection to the database, which is set up in the tests' setUp method.