vmalloc/mongomock — pull request #4 by ca77y (2012-08-05 22:36:06+00:00)
Title: fix for ObjectId.__str__ to return str

Hi,

Firstly, many thanks for starting this project.

A small fix to ObjectId as right now it raises an error:
```TypeError: __str__ returned non-string (type UUID)```
and the optional 'id' argument for a constructor to be in line with bson ObjectId

Cheers,
catty