Adds line breaks before and after the given node if the previous and next siblings
aren't already causing a visual line break (block element or <br>)
function _addLineBreakBeforeAndAfter(node) {
    var doc             = node.ownerDocument,
        nextSibling     = _getNextSiblingThatIsNotBlank(node),
        previousSibling = _getPreviousSiblingThatIsNotBlank(node);

    if (nextSibling && !_isLineBreakOrBlockElement(nextSibling)) {
      node.parentNode.insertBefore(doc.createElement("br"), nextSibling);
    }
    if (previousSibling && !_isLineBreakOrBlockElement(previousSibling)) {
      node.parentNode.insertBefore(doc.createElement("br"), node);
    }
  }