Missing values when displaying Multi-index after groupby in notebook
#### Code Sample, a copy-pastable example if possible

```python
df = pd.DataFrame({'a':[True, False, False, True], 'b':[True, True, False, False], 'c': [1,2,3,4], 'd':[1,1,1,1]})
df_count = df.groupby(['c','a','b']).count()
```
I get 

![image](https://user-images.githubusercontent.com/7989822/42571064-43d92ee8-8516-11e8-957f-b19ffad8b071.png)

which is correct

However if i unstack the two levels corresponding to 'a' and 'b'

```python
df_count.unstack([1,2])
```

I get this

![image](https://user-images.githubusercontent.com/7989822/42571153-85032aae-8516-11e8-9c27-abbbb9e62f4f.png)

#### Problem description

For an unknown reason the 'False' label is missing on the 'a' line and there's no shade to indicate a group so it make the result very difficult to interpret.


#### Output of ``pd.show_versions()``

INSTALLED VERSIONS
------------------
commit: None
python: 3.6.1.final.0
python-bits: 64
OS: Windows
OS-release: 10
machine: AMD64
processor: Intel64 Family 6 Model 94 Stepping 3, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: None.None

pandas: 0.21.0
pytest: 3.5.1
pip: 10.0.1
setuptools: 28.8.0
Cython: None
numpy: 1.14.5
scipy: 1.1.0
pyarrow: None
xarray: None
IPython: 6.3.1
sphinx: None
patsy: None
dateutil: 2.7.3
pytz: 2018.4
blosc: None
bottleneck: None
tables: None
numexpr: None
feather: None
matplotlib: 2.2.2
openpyxl: 2.5.4
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 1.0.2
lxml: 4.1.1
bs4: None
html5lib: 1.0.1
sqlalchemy: 1.1.15
pymysql: None
psycopg2: 2.7.4 (dt dec pq3 ext lo64)
jinja2: 2.10
s3fs: 0.1.0
fastparquet: None
pandas_gbq: None
pandas_datareader: None

</details>
