Apply styles to classes instead of tags

[benash]

Thanks for this fantastic project. I'm noticing that the styles that are applied directly to label (and perhaps other tags) can make it difficult to integrate halfmoon with existing projects. For now, I can do my best to adjust variables like --label-margin-bottom, but I was wondering if it might make more sense to shift these styles to classes like .label so they're more opt-in. What do you think?