1.4.0 version
Remove deprecated string interpolation
Correct handling of units.

width: 1cm - 5mm
=> width: 0.5cm (instead of -4cm)

@ratio: 100px/50px
=> @ratio == 2 (instead of 2px)
loosened restriction on css units (who knows what W3C will think up next)
Add Sass like extend
Fix bug global leaks, `;` to `,`
Fix combinator is not extended
Fix merge errors/problems and change format to ++
- Change the default behavior of "@import" to only import once.
- Add @import-multiple if for some insane reason you want multiple imports.
- Continue to support @import-once for backwards compatibility.
- Fixes #212.
Change extend format to :extend(.class); - part 1 - support for stand-alone &:extend(.class);
Fix unit comparing after merge
Rudimentary support for extend in selectors
Add additional test for nested selectors. Rebuild dist.
Correct unit merge
regenerate browser files