add function 'get_all_feeds' to FeedList, FeedCategory
get_all_feeds returns `set`
Merge pull request #7 from Kjwon15/feedlist

FeedList.get_all_feeds() function
Merge branch 'crawler' of https://github.com/viobo/libearth into viobo-crawler
If outline element has children(s) and not 'xmlUrl' that is a FeedCategory, not a Feed.
Logo artwork  [ci skip]
Logo artwork on readme  [ci skip]
Raise the logo art on readme
Remove a radiant line
Use opener instead of httpretty module