BLD: Nosetests failures on 32-bit (test_first_last_nth_dtypes, test_iloc_getitem_array)
I'm getting them on two different 32-bit ubuntu machines updated to master (0.11.0.dev-5f2ec15)...I'm guessing these are 32-bit specific since they're `dtype` related:

```
======================================================================
FAIL: test_first_last_nth_dtypes (pandas.tests.test_groupby.TestGroupBy)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/stephen/Projects/pandas/pandas/tests/test_groupby.py", line 176, in test_first_last_nth_dtypes
    assert_frame_equal(first, expected, check_names=False)
  File "/home/stephen/Projects/pandas/pandas/util/testing.py", line 217, in assert_frame_equal
    check_less_precise=check_less_precise)
  File "/home/stephen/Projects/pandas/pandas/util/testing.py", line 185, in assert_series_equal
    assert(left.dtype == right.dtype)
AssertionError

======================================================================
FAIL: test_iloc_getitem_array (pandas.tests.test_indexing.TestIndexing)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/stephen/Projects/pandas/pandas/tests/test_indexing.py", line 345, in test_iloc_getitem_array
    self.check_result('array like', 'iloc', s.index, 'ix', { 0 : [2,4,6], 1 : [3,6,9], 2: [4,8,12] }, typs = ['ints'])
  File "/home/stephen/Projects/pandas/pandas/tests/test_indexing.py", line 249, in check_result
    _eq(t, o, a, obj, key1, k2)
  File "/home/stephen/Projects/pandas/pandas/tests/test_indexing.py", line 206, in _eq
    raise AssertionError(_print('type error'))
AssertionError: None
```

I can look into this and resolve this myself if no one else does, but just wanted to throw it out there first (knee deep in other stuff atm...)
