use `./` for all relative path imports (play nice with atomify/npm-less)

Created by: spacepluk

I'm trying to use bootstrap with atomify, and if I try to import bootstrap's less files like this...

@import 'bootstrap/less/bootstrap.less';

...it fails because npm-less gets "confused" and interprets the file names as module names.

This patch in bootstrap solves the problem while allowing npm-less to keep a more consistent behavior.