blockHeader function improvement

[doiftrue]

Look to this example, assume we trying to parse this header:
### #header text
We get <h3>header text</h3> but not <h3>#header text</h3> as it's on github or anywhere else. It's because of this line in blockHeader function:

$text = trim($Line['text'], '# ');

I suggest replace it with two lines:

$text = trim($Line['text'], '#');
$text = trim($text);

Thanks for code and hope you repair this in next release.

[kminchev]

Workaround is \#header

[doiftrue]

Thanks, I know about \#header but it's bad option for me. I make wrapper class for parsedown and add my blockHeader method.

For example here on github if a write ### #header I get #header not header and I think it's more correctly.

[erusev]

@doiftrue it is indeed more correct - i'll fix it as soon as i get a chance

[doiftrue]

Thanks a lot!

[praveenscience]

Guess in simple terms, we can make it using double trim() like this:

$text = trim(trim($Line['text'], '#'));

[aidantwoods]

Looks like I added an equivalent fix in #583, this will be in the next version :)