Add literal tabs to parser.
Have Docx reader properly interpret tabs.
Introduce blockNormalize

This will help take care of spaces introduced at the beginning of strings.
Fix notes test.

This previously allowed spaces at the beginning of a paragraph.
Add tabs tests.
Merge pull request #1354 from jkr/literalTab

Parse literal tabs in docx
HTML reader:  Allow space between `<col>` and `</col>`.

Test case:

```
<table border="1">
  <colgroup>
    <col> </col>
    <col></col>
  </colgroup>
  <tbody>
    <tr>
        <td>X</td>
        <td>Y</td>
    </tr>
    <tr>
        <td>1</td>
        <td>2</td>
    </tr>
  </tbody>
</table>

```
Docx writer:  Use Compact style for empty table cells.

Otherwise we get overly tall lines when there are empty
table cells and the other cells are compact.

Closes #1353.