Default to http for DDG bridge

Because some hosts do not support https.
Corrected default number of articles in CryptomeBridge.

The bridge was outputting a single entry when parameter n was empty.
Changed default number of article from 90 to 20 in CryptomeBridge.
Removed non-working bridges
Added parameter check of OpenClassRooms.
Added parameters checks for PinterestBridge
Added Bandcamp

Merged manually from https://github.com/sebsauvage/rss-bridge/pull/24
Small update on README.md
Updated README.md
Merge pull request #2 from sebsauvage/master

merge upstream