Change default scale for `modular-scale` function

[whmii]

Currently the default scale for the modular-scale function is Perfect Fourth (1.333). This is a pretty drastic scale and seems unlikely as a default typographic system. See http://modularscale.com/?1&em&1.25

I think it would make sense to switch the default value to something that can be more easily controlled out of the box. While it in not a large adjustment, I think Major Third (1.25) would be a better default. See http://modularscale.com/?1&em&1.25

[tysongach]

Yeah, good call.

I’ve always found myself changing this to be less drastic, usually to either $major-second or $major-third. PR opened!

[tysongach]

Merged for 5.0

[whmii]

muchas grasses