Sub/sup should not be reset in the first place

[Petah]

Sub/sup should not be reset in the first place, i.e. you are resetting the reset.

https://github.com/PANmedia/OnionKnight/blob/master/base/tags.scss#L158-L164

[tbredin]

If we want to fix this we'll need to write our own (limited) reset, as this comes from the compass reset.

However, this currently leaves us with sup/sub tags that are nicely normalised across browsers, I don't see this being a big issue unless you're wanting to set further styles on these tags (do we really need to?)