Compute column width using DisplayWidth

I was confused by the column widths:

![image](https://cloud.githubusercontent.com/assets/438648/5515226/d537c560-8859-11e4-9196-3baed414e30a.png)

This pull request fixes that. I don't know if the fix is optimal or not, but this PR can serve as an issue instead if not.

![image](https://cloud.githubusercontent.com/assets/438648/5515229/f8466ea8-8859-11e4-9b86-d8d05ed990e4.png)