Add automatic type scaling based on modular scales

[Cleecanth]

Using modular scale principles (http://alistapart.com/article/more-meaningful-typography), I added the option for automatic heading scaling.

This still uses the typecsset base functions/mixins, but allows the user to create a typographic scale for slightly more harmonious type scaling.

Some of this might be able to be cleaned up, but the functions work as suggested.

Future possibility:

• Make the modular-scale function available via a mixin (or variable list) to allow users access to their scale outside of just headings.

[mmadden]

Funny, I just started using typcecsset in a new project last night and also integrated https://github.com/Team-Sass/modular-scale (2.x) to do exactly this (applying modular scales to headings, etc.).

There are two things I really like about the modular-scale (2.x) project that I'd like typecsset to play nice with or replicate:

• I can use the ms(n) function anywhere I need to apply the scale to other elements (e.g. table cell padding).
• The scale is easily changed using named-constants or the decimal value (e.g. $minor-seventh or 1.778).

Even more awesome would be having functions to convert to/from pixel/rem units, and add leading/trailing line spaces (with pixel fallbacks) to arbitrary elements to maintain the baseline when applying modular scales.

[Cleecanth]

I'll be adding a commit tomorrow to expose the modular scale as a mixin that can be used for any property.

Something like (where 1 is the desired scale increment):

p { @include modular-scale( 1 , margin-left ); }

Which would output to something like:

p { margin-left: 21px; margin-left: 1.3125rem; }

Using negative numbers will allow you to go down the scale (just a nice side effect of the algorithm).

[mmadden]

@Cleecanth, I look forward to seeing how this turns out.

What do you think about specifying the $typecsset-ratio as an integer instead? (e.g. the scale values shown at http://type-scale.com/)