fix for #41

[jcolson]

[dwrolvink]

Good idea, but might give issues in the future when people add images to the header using their own template. Also by using width it negatively effects small images by stretching them.

This would be better:

.container img {
    max-width: 100%;
}

This limits the effect to container divs (which always enclose note content), and does not stretch small images.