remove isEmptyTextNode check

[kdojeteri]

I suggest this as a fix for #39

---

To be honest, I don't even know why you would assume that only specifically whitespace nodes with newlines are empty. Yet that's what the code says.

export default function isEmptyTextNode(node) {
  return node.type === 'text' && /\r?\n/.test(node.data) && node.data.trim() === '';
}

[coveralls]

Coverage remained the same at 100.0% when pulling 042af2a on Peping:master into f28597e on wrakky:master.