add extractors/css.py js.py
add html.py class LinkExtractor(BaseRegexExtractor)
add find_between function, between two string
add class MarkdownExtractor(BaseExtractor)
make sure pos1 is not -1, and s2 is behind s1
name error
add function build_valid_filename
log errors into self.errors
str(i)
add utils module
add utils/html.py
pre class="prettyprint lang-py" -->get pre
a tag, errors log info
MarkdownExtractor(BaseExtractor).extract reuse nlp.utils.html.html2markdown