category id of root treated as valid
Erase the unused constant
APIs which return feed entries and which return a feed entry combined

No matter what the category context is
Get updated tag data, not published tag data
Title was not given when return an entry content
Get all feeds return feeds and categories separately
Correct mistyped the entry id of test xmls
Adjust tests for the changes accompanied by the change of get_all_feeds
Combine APIs which context were different but work same
Adjust coding style
PEP 8