Quantifiers

[rodricios]

Moving node_text_length and children_counter to their own submodule will hopefully do two things:

1. Standardize - protocol is simple:
   • input: node (lxml.html.HtmlElement and sometimes *._ElementTree)
   • output: quantity or quantities (numerical or collections.Counter)
2. Modularize - the bigger goal of creating a truly functional lib is still pretty unclear, but this branch will hopefully simplify a user's experience in creating custom pipelines:

Consider:

from libextract.html.tabular import children_counter
from libextract.html.article import node_text_length

vs.

from libextract.quantifiers import children_counter, text_length

Partially addresses issue #1

[eugene-eeo]

Man, this is good. I'll review the code before merging.