Snipcart less theme

There is still some work to do to make it a lib.
Extract our own styles and only keep colors, fonts and tweaks to snipcart.

I disabled minifying for easier debugging. Forgot to enable it back...
Have you thought about a mixin for the cross-browsers versions of box-shadow? You could add a box-shadow mixin that takes 5 parameters like this:
```.box-shadow(@top, @right, @bottom, @left, @color) {
  -webkit-box-shadow: @top @right @bottom @left @color;
  -moz-box-shadow: @top @right @bottom @left @color;
  box-shadow: @top @right @bottom @left @color;
}```
and use it like this:
```box-shadow(0px, 2px, 2px, 0px, rgba(0, 0, 0, 0.5));```