Slicing on DatetimeIndex throws KeyError: [int] not found
#### Code Sample, a copy-pastable example if possible

Unfortunately can't reproduce it with other examples. Only this which I load from csv.
![image](https://cloud.githubusercontent.com/assets/674200/15042375/893f4f52-12c3-11e6-9e18-96892b53035e.png)

`txn.loc[pd.Timestamp('2014-06-04 00:00:00'):]`

``` ---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
<ipython-input-35-ce3d2db63a82> in <module>()
----> 1 txn.loc[pd.Timestamp('2014-06-04 00:00:00'):]

/opt/miniconda/lib/python2.7/site-packages/pandas/core/indexing.py in __getitem__(self, key)
   1284             return self._getitem_tuple(key)
   1285         else:
-> 1286             return self._getitem_axis(key, axis=0)
   1287 
   1288     def _getitem_axis(self, key, axis=0):

/opt/miniconda/lib/python2.7/site-packages/pandas/core/indexing.py in _getitem_axis(self, key, axis)
   1398         if isinstance(key, slice):
   1399             self._has_valid_type(key, axis)
-> 1400             return self._get_slice_axis(key, axis=axis)
   1401         elif is_bool_indexer(key):
   1402             return self._getbool_axis(key, axis=axis)

/opt/miniconda/lib/python2.7/site-packages/pandas/core/indexing.py in _get_slice_axis(self, slice_obj, axis)
   1306         labels = obj._get_axis(axis)
   1307         indexer = labels.slice_indexer(slice_obj.start, slice_obj.stop,
-> 1308                                        slice_obj.step, kind=self.name)
   1309 
   1310         if isinstance(indexer, slice):

/opt/miniconda/lib/python2.7/site-packages/pandas/tseries/index.py in slice_indexer(self, start, end, step, kind)
   1503 
   1504         try:
-> 1505             return Index.slice_indexer(self, start, end, step, kind=kind)
   1506         except KeyError:
   1507             # For historical reasons DatetimeIndex by default supports

/opt/miniconda/lib/python2.7/site-packages/pandas/indexes/base.py in slice_indexer(self, start, end, step, kind)
   2698         """
   2699         start_slice, end_slice = self.slice_locs(start, end, step=step,
-> 2700                                                  kind=kind)
   2701 
   2702         # return a slice

/opt/miniconda/lib/python2.7/site-packages/pandas/indexes/base.py in slice_locs(self, start, end, step, kind)
   2877         start_slice = None
   2878         if start is not None:
-> 2879             start_slice = self.get_slice_bound(start, 'left', kind)
   2880         if start_slice is None:
   2881             start_slice = 0

/opt/miniconda/lib/python2.7/site-packages/pandas/indexes/base.py in get_slice_bound(self, label, side, kind)
   2826             except ValueError:
   2827                 # raise the original KeyError
-> 2828                 raise err
   2829 
   2830         if isinstance(slc, np.ndarray):

KeyError: 1401840000000000000
```
#### Expected Output

Slice of everything after '2014-06-04 00:00:00'.
#### output of `pd.show_versions()`

```
INSTALLED VERSIONS
------------------
commit: None
python: 2.7.11.final.0
python-bits: 64
OS: Linux
OS-release: 3.13.0-77-generic
machine: x86_64
processor: x86_64
byteorder: little
LC_ALL: en_US.UTF-8
LANG: en_US.UTF-8

pandas: 0.18.0
nose: 1.3.7
pip: 8.1.1
setuptools: 20.7.0
Cython: 0.23.4
numpy: 1.11.0
scipy: 0.17.0
statsmodels: 0.6.1
xarray: None
IPython: 3.2.1
sphinx: 1.3.1
patsy: 0.4.0
dateutil: 2.5.3
pytz: 2016.4
blosc: None
bottleneck: 1.0.0
tables: 3.2.2
numexpr: 2.4.3
matplotlib: 1.5.1
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: 4.3.2
html5lib: None
httplib2: None
apiclient: None
sqlalchemy: 1.0.8
pymysql: None
psycopg2: 2.6.1 (dt dec pq3 ext)
jinja2: 2.8
boto: 2.30.0
```
