[this mixin](https://github.com/pmsipilot/ui/blob/master/less/utils.less#L62-L65) is in conflict w/ twitter bootstrap [opacity](https://github.com/twbs/bootstrap/blob/master/less/mixins/opacity.less) several solutions : - rename the mixin (eg. .ui-opacity()) - add twitter bootstrap as a deps - mark this as incompatible w/ twitter bootstrap