Related TypeErrors in multi-indexed DataFrame
## Code sample

``` python
import pandas as pd
import numpy as np

foo = pd.DataFrame(np.arange(100).reshape((10,10)))
bar = pd.DataFrame(np.arange(100).reshape((10,10)))

df = pd.concat({
        'foo': foo.stack(),
        'bar': bar.stack()
    }, axis=1)

df.index.names = ['fizz','buzz']
```
## Output

``` python
> df
TypeError: data type "fizz" not understood

> df_ = df.set_index('foo', append=True)  # shouldn't call __repr__
TypeError: data type "fizz" not understood

> df[:61]
TypeError: data type "fizz" not understood

> df[:60]
           bar  foo
fizz buzz          
0    0       0    0
     1       1    1
     2       2    2
...
```
## show_versions() output

```
> pd.show_versions()

INSTALLED VERSIONS
------------------
commit: 2ba977a917ac5c092378a2f172f59d53b14de968
python: 3.5.1.final.0
python-bits: 64
OS: Darwin
OS-release: 15.3.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: None
LANG: en_US.UTF-8

pandas: 0.18.0+111.g2ba977a
nose: None
pip: 8.1.1
setuptools: 20.6.7
Cython: 0.24
numpy: 1.11.0
scipy: 0.17.0
statsmodels: None
xarray: None
IPython: 4.1.2
sphinx: None
patsy: None
dateutil: 2.5.2
pytz: 2016.3
blosc: None
bottleneck: None
tables: None
numexpr: None
matplotlib: 1.5.1
openpyxl: None
xlrd: None
xlwt: None
xlsxwriter: None
lxml: None
bs4: None
html5lib: None
httplib2: 0.9.2
apiclient: 1.5.0
sqlalchemy: None
pymysql: None
psycopg2: 2.6.1 (dt dec pq3 ext lo64)
jinja2: 2.8
boto: None
pandas_datareader: None
```
