css text sizing

Modular scale

• http://thesassway.com/advanced/modular-css-typography
• http://alistapart.com/article/more-meaningful-typography
• http://modularscale.com/scale/?px1=16&px2=&ra1=1.6&ra2=0
• http://bourbon.io/docs/#modular-scale
• http://blog.8thlight.com/billy-whited/2011/10/28/r-a-ela-tional-design.html#tips