df.plot.bar not showing colors as expected as compared to matplotlib
https://github.com/pandas-dev/pandas/blob/3a7f956c30528736beaae5784f509a76d892e229/pandas/plotting/_core.py#L2649-L2666

```python
import pandas as pd
import numpy as np
import matplotlib
get_ipython().magic(u'pylab inline')

# In[17]:
df = pd.DataFrame({'id': range(1,11), 'normcolor': np.random.rand(10), 'count': np.random.randint(0,100,(10))})

# In[21]:
colors = matplotlib.cm.hsv(df['normcolor'])
df.plot.bar('id','count', color=colors) # return plot with not color variation


# In[22]:
plt.bar(df['id'], df['count'], color=colors) # returns plot as expected
```

# Current Output
![image](https://user-images.githubusercontent.com/6607313/29251984-dabee23e-807c-11e7-80a3-bd3d57cfefba.png)

# Correct Output
![image](https://user-images.githubusercontent.com/6607313/29251985-e421e4e8-807c-11e7-9fb0-f68da61a8089.png)

