Timestamp.min and .max return a Python datetime object that is not a valid Timestamp
```
import pandas as pd

pd.Timestamp(pd.Timestamp.min)
```

Throws: ValueError: Out of bounds nanosecond timestamp: 1-01-01 00:00:00

Pandas version: 0.11.1_dev
Numpy version: 1.7.1

The the min and max methods on the Timestamp class return simple Python datetime objects, but more importantly they do not adhere to the limitations of Timestamps. They return the default datetime(1,1,1) and datetime(9999, 12, 31, 23, 59, 59, 999999) respectively - both of which are well outside of the valid Timestamp range.
