No change required to upgrade to multiple databases. Aliases are used
to describe the database and these can be manually registered or fall
through to a default alias using connect.
Made get_connection and get_db first class members of the connection class.
Old style _get_connection and _get_db still supported.
Refs: #84#87#93#215
The API is similar to that of PyMongo and most of the same operations are
possible.
The FileField can be written too with put(), write() or by using the assignment
operator. All three cases are demonstrated in the tests. Metadata can be added
to a FileField by assigning keyword arguments when using put() or new_file().
