fix: ensure all text is maintained in html output

[MthwRobinson]

Summary

Fixes a bug introduced in #313 and closes #332 . Strip script elements from the XML document rather than skipping them in the iteration step. The switch from tag_elem.itertext() to tag_elem.iter() had caused some text to be missed.

Testing

The following should show a full paragraph of text output now:

from unstructured.partition.html import partition_html

url = "http://paulgraham.com/getideas.html"
elements = partition_html(url=url)
print("\n\n".join([str(el) for el in elements]))

[LaverdeS]

Nice addition. Maybe better to have also one of these in the main repo?