GitHub Markdown tables with no rows don't get converted to Html tables

[csuzw]

Executing pandoc -f markdown_github -t html5 test.md where test.md is:

### Arguments

| Name | Type | Description | Example |
|------|------|-------------|---------|

### Example

Outputs the following html:

<h3 id="arguments">Arguments</h3>
<p>| Name | Type | Description | Example |<br />|------|------|-------------|---------|</p>
<h3 id="example">Example</h3>

As the markdown table gets displayed correctly on GitHub wiki, I'd expect the html to contain a table, rather than the table text wrapped in <p> tags.

[lierdakil]

This should be as simple as changing many1 to many in Markdown pipe table parser. See 84dfff8. Shouldn't break anything.