Add section on ratios and aesthetic sensitivities of tachyons

[iteles]

Having been created by a designer, there is a lot of care given to having the correct ratios for a pleasing layout as well as readable/accessible content out of the box with tachyons.

Not only does it promote consistency, but it promotes aesthetic harmony.

Good design is based on math. Certain patterns and ratios are so prevelant in nature and music that they can't be denied as elegant design solutions.

I suggest that this is worth a mention, particularly as something for developers to note when working closely with designers.

[nelsonic]

@iteles this would be a really useful addition for beginners.