Error bars not rendered correctly
#### Code Sample, a copy-pastable example if possible

From the `/doc/source/visualization.rst`:

```python
import pandas as pd
import matplotlib.pyplot as plt

# Generate the data
ix3 = pd.MultiIndex.from_arrays([['a', 'a', 'a', 'a', 'b', 'b', 'b', 'b'], ['foo', 'foo', 'bar', 'bar', 'foo', 'foo', 'bar', 'bar']], names=['letter', 'word'])
df3 = pd.DataFrame({'data1': [3, 2, 4, 3, 2, 4, 3, 2], 'data2': [6, 5, 7, 5, 4, 5, 6, 5]}, index=ix3)

# Group by index labels and take the means and standard deviations for each group
gp3 = df3.groupby(level=('letter', 'word'))
means = gp3.mean()
errors = gp3.std()
means
errors

# Plot
fig, ax = plt.subplots()
means.plot.bar(yerr=errors, ax=ax)
```
#### Problem description

The resulting image doesn't contain the horizontal ticks of the error bars.

![figure_1](https://user-images.githubusercontent.com/2905978/30180792-66d8d80e-9411-11e7-98fb-4510c4650f63.png)


#### Expected Output

![figure_1](https://user-images.githubusercontent.com/2905978/30180607-c03ccfaa-9410-11e7-8a01-b5ffd628f472.png)

To achieve this the last line should be replaced with

```
means.plot.bar(yerr=errors, ax=ax, capsize=4)
```

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

<details>

INSTALLED VERSIONS
------------------
commit: None
python: 3.6.2.final.0
python-bits: 64
OS: Darwin
OS-release: 16.7.0
machine: x86_64
processor: i386
byteorder: little
LC_ALL: en_US.UTF-8
LANG: en_US.UTF-8
LOCALE: en_US.UTF-8

pandas: 0.20.3
pytest: 3.2.1
pip: 9.0.1
setuptools: 27.2.0
Cython: 0.26
numpy: 1.13.1
scipy: 0.19.1
xarray: None
IPython: 6.1.0
sphinx: 1.6.3
patsy: 0.4.1
dateutil: 2.6.1
pytz: 2017.2
blosc: None
bottleneck: 1.2.1
tables: 3.4.2
numexpr: 2.6.2
feather: None
matplotlib: 2.0.2
openpyxl: 2.4.8
xlrd: 1.1.0
xlwt: 1.3.0
xlsxwriter: 0.9.8
lxml: 3.8.0
bs4: 4.6.0
html5lib: 0.999
sqlalchemy: 1.1.13
pymysql: None
psycopg2: None
jinja2: 2.9.6
s3fs: None
pandas_gbq: None
pandas_datareader: None
</details>
