Remove return value in one __ini__

It was some kind of previous code left-over
Use HTTP Accept headers

Tries to tell servers what we need, hopefull this will avoid the useless donwloading of pdf, images and so on (especially on Hacker News)
Make sure final data is there in downloader
Add "txt" argument, to change HTTP Content-Type
Use "str.startswith" instead of ugly hack
Reddit: check feed url instead of link url