Remove unnecessary string interpolations
hide-text for non-English Characters

This approach will not work perfectly if line-height is 1 for Japanese. (maybe Chinese also).
Fix deprecated golden-ratio to work with new modular-scale
Changes -ms-flex-pack from center to distribute

- Fixes #426
- Fixes indentation
Removes prefixer from border radius shorthand mixin
Update bower.json ignore since #480

Since ./dist is removed, app is necessary for importing the files
when bourbon is loaded via bower, thus shouldn't be ignored.
Allow hide-text addon to accept height argument

- Fixes #551
Cleans up clearfix mixin
Refines meta info for Bourbon gem
Refine docs

- Fixes #488
Add validate-length function
Add validate-size function
Refactor size addon

- Allow auto, inherit, initial values
- Allow unitless number values
- Allow intrinsic sizing values
- Fixes #391
- Fixes #468