Merge pull request #2 from rnarius/master

remove margin from media elements
add hdpi mixin
add retina-image mixin
update usage examples
include normalize.scss
gruntconf & tests setup
Merge pull request #3 from rnarius/feature/retina-image

add hdpi mixin & retina-image mixin
gitignore & version bump
Merge branch 'testenv'
Merge remote-tracking branch 'origin/master'