First commit for feed.py
basic functions to feed list
fix function args, add test codes
fix docstring for valid Sphinx syntax
add feed.rst
change data type, adjust code. and remove `__repr__` function
now feed.py can read OPML file.
add test function for feed.py, add file notfound exception
change variable name use underscore
class `feed` is able to working with XML string
adjust coding style pep8