offset-top=0 and offset-bottom=0 don't work on affix plugin via data attributes
Created by: tarot
Via JavaScript, affix plugin can accept {offset:{top:0, bottom:0}} options.
But via data attributes,
<nav data-spy="affix" data-offset-top="0" data-offset-bottom="0">...</nav>
means
<nav data-spy="affix">...</nav>
Probrem in: https://github.com/twbs/bootstrap/blob/master/js/affix.js#L130-L131
Expected:
if (data.offsetBottom != null) data.offset.bottom = data.offsetBottom
if (data.offsetTop != null) data.offset.top = data.offsetTop