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...
I checked a little, and both seem nice apart from the fact that none has a build success. I don't really mind one or another and unfortunately I'm missing time to dig further so I'll leave the choice up to you. I think having a lib like that to handle css prefixes is a good idea though.