Fix for transform-tabular-data on empty fields

When the field is empty, f['#text'] raises a KeyError.
This is due to the way xmltodict parses:
    when the field in an xml tag is empty, '#text' is not defined
Use f.get('#text', None) instead.
A test have been added to check this.
Update documentation
Add documentation to transform_tabular_data
Fix for getting incomplete types of table

Incomplete table includes:
    1. Tables with 1 row - this is a special case because single fields
    will be parsed into a dict, rather than a list as expected by the
    previous list comprehension
    2. Rows with empty fields
    3. Empty tables - this fails previously, but will return an empty
    dict now

Unit tests for each of these cases have also been written
Bumping version.
pypi script.
Update README.md

Adding downloads badge.
Merge pull request #13 from ngzhian/transform-tabular-data-fix

Fix for transform-tabular-data on empty fields
Update CHANGES

Added new version
Version 0.4.1