plot.bar misalignment when width=1
Two minor issues with the width optional argument of plot.bar() in Pandas 0.18.0:

1) Using width=1 (integer) causes misalignment of the x-axis

``` python
import pandas as pd
import numpy as np
df = pd.DataFrame(np.random.random((6, 5)) * 10, index=list('abcdef'), columns=list('ABCDE'))
df.plot.bar(stacked=True, width=1)
```

![figure_1](https://cloud.githubusercontent.com/assets/1150402/14782442/ade46c52-0ae9-11e6-9b90-729d413861d1.png)

Compare this with the correct behaviour when defining width as a float:

``` python
df.plot.bar(stacked=True, width=1.)
```

![figure_2](https://cloud.githubusercontent.com/assets/1150402/14782452/b29a70fc-0ae9-11e6-9b72-031fccc5714f.png)

2) Using width=None causes a TypeError, where I would expect the default behaviour.
