`tab_length` parameter ignored

[karepker]

Input file:

* Test 1
  * Test A
  * Test B
* Test 2

run with markdown.markdownFromFile('input.md', tab_length=2) produces output file:

<ul>
<li>Test 1</li>
<li>Test A</li>
<li>Test B</li>
<li>Test 2</li>
</ul>

when it should produce a nested list.

I think I've found the issue. In markdown/blockprocessors.py line 304:

RE = re.compile(r'^[ ]{0,3}\d+\.[ ]+(.*)')

3 should be self.tab_length - 1. Similarly for CHILD_RE and INDENT_RE in OListProcessor, RE in UListProcessor, and CHILD_RE in both SaneOListProcessor and SaneUListProcessor.

When I make these changes locally, I get the expected output for my test case, and all other tests pass as well. See this commit in my fork of your repository.

I can send you a pull request with these changes if you'd like.

[waylan]

A pull request is welcome.