BUG: scatter_matrix draws incorrect axis
Closes #5662. Refactored a little.

Made examples to confirm 1st and 2nd row's yaxis are identical.

```
import pandas as pd
import numpy as np
df = pd.DataFrame(np.random.randn(100, 3))
df[0] = df[1]
pd.tools.plotting.scatter_matrix(df)
```

![figure_1](https://cloud.githubusercontent.com/assets/1696302/6092365/63f4ce98-af1e-11e4-9175-eba45b483bba.png)

```
df[1] = df[1] / 3 - 2
df[0] = df[1]
pd.tools.plotting.scatter_matrix(df)
```

![figure_2](https://cloud.githubusercontent.com/assets/1696302/6092366/68041dea-af1e-11e4-8ecd-cfcb33aaf1a9.png)

@sinhrks is there actually anything that prevents this from being merged?
cc @TomAugspurger 
 No, I think this is ready for review. Because it is categorized as a bug fix, is it possible to include it in 0.16.1 (not next major release)?

I'll rebase this later to fix the release note.
 Thanks. Ping me when the rebase is done and I'll get it merged. 

> On Mar 30, 2015, at 22:18, Sinhrks notifications@github.com wrote:
> 
> No, I think this is ready for review. Because it is categorized as a bug fix, is it possible to include it in 0.16.1 (not next major release)?
> 
> I'll rebase to in this later to fix the release note.
> 
> —
> Reply to this email directly or view it on GitHub.
 @TomAugspurger Rebased, and now green.
 OK, thanks!
