code: function getTagName(dom, skipDataIs) {
    var child = getTag(dom),
      namedTag = !skipDataIs && getAttr(dom, IS_DIRECTIVE);
    return namedTag && !tmpl.hasExpr(namedTag) ?
                  namedTag :
                child ? child.name : dom.tagName.toLowerCase()
  }
docs: Get the tag name of any DOM node
  @param   { Object } dom - DOM node we want to parse
  @param   { Boolean } skipDataIs - hack to ignore the data-is attribute when attaching to parent
  @returns { String } name to identify this dom node in riot