applymap returns empty list even though function is boolean
Weird behaviour with apply map, the below function should always return a bool.

```
In [11]: df = pd.DataFrame({'feat 1': {0: [], 1: 6, 2: None}, 'feat 2': {0: [], 1: 8, 2: 10}, 'feat 3': {0: 5.0, 1: 3.0, 2: np.nan}})

In [14]: df.applymap(lambda x: x == [] or x is None)
Out[14]:
  feat 1 feat 2 feat 3
0   True   True  False
1  False  False  False
2   True  False  False

In [15]: df.applymap(lambda x: x is None or x == [])
Out[15]:
  feat 1 feat 2 feat 3
0   True   True     []
1  False  False     []
2   True  False     []
```

Strange use case, but maybe there is something weird here.

http://stackoverflow.com/questions/22124537/read-json-populates-with-empty-lists-how-to-remove-those-rows/22124735#22124735
