Resolve issues with rendering in firefox

[jwildfire]

No description provided.

[samussiah]

Give the chart container elements an explicit width.

[emmorris]

The thumbnails in the visual test suite do not render well in Firefox. Some of them just display as a blank box while others display with strange proportions, but you can view them if you click the "Show Large Version" button for each one.

Spencer suggested a fix in his comment above. Might be worth going ahead and fixing to increase efficiency.