DataFrame.boxplot() ignored figsize keyword
The [DataFrame.boxplot](http://pandas.pydata.org/pandas-docs/version/0.17.1/generated/pandas.DataFrame.boxplot.html) reference documentation says I can change the size of a plot though the `figsize` keyword, but this appears not to work.

Using `df.plot(kind='box')` does respect `figsize`.

```
import pandas as pd
import numpy as np
import matplotlib.pyplot as plt
import sys

print("pandas version = {}".format(pandas.__version__))
print("python version = {}".format(sys.version))
df = pd.DataFrame(np.random.rand(10, 5), columns=['A', 'B', 'C', 'D', 'E'])
df.plot(kind='box', figsize=(12,8))
plt.show()

df.boxplot(return_type='axes', figsize=(12,8))
plt.show()
```

![screen shot 2016-01-04 at 6 02 34 pm](https://cloud.githubusercontent.com/assets/295428/12105825/6a9748c2-b30d-11e5-876c-9c4ade88976d.png)
