Commercial comps tweaks2

This tidies up a load of small issues with Masterclasses and Soulmates.

Widths are now calculated when using 1/3 & 2/3, makes it far better than 33% & 66%.

Mixins made for duplicated code used in Masterclasses component.
To support old Androids, you might want to add the `-webkit` version of this property, and specify width and height for it.

http://caniuse.com/#search=background-size