TypeError: DataShape time is not NumPy-compatible

Hi,

I have some problems when interfacing with MongoDB. Namely, I can do this

`In [104]: odo(traffic, 'mongodb://localhost:27017/packt::traffic')`

`Out[104]: Collection(Database(MongoClient('localhost', 27017), 'packt'), 'traffic')`

but when I try to read it back

`In [105]: traffic_mongo = bl.Data('mongodb://localhost:27017/packt::traffic')`

`traffic_mongo.head()`

I get the error as in the subject. The `traffic` object is of blaze.Data() type and contains two date fields.