pd.Timestamp("now") returns oddly
I would expect these two return the same:

```
In [10]: pd.Timestamp.now()

Out[10]:
Timestamp('2014-02-24 17:54:18.370128', tz=None)

In [11]: pd.Timestamp("now")

Out[11]:
Timestamp('2014-02-24 22:54:18', tz=None)
```
