BUG: DataFrame with tz-aware data and max(axis=1) returns NaN
I have a dataframe looks like this, and its column 2 is missing:
![image](https://cloud.githubusercontent.com/assets/6269369/8245984/6ff1798c-1669-11e5-88b1-2c27a6b5f2fb.png)

When I try to select the max date in each row, I got all NaN in return:
![img2](https://cloud.githubusercontent.com/assets/6269369/8246090/eea64bbc-166a-11e5-9fb3-668a37a2cf3a.png)

However, If the dataframe's type is float64, the selection work as expected.
