add new comment sources info to make file #2768

#2768

### Changes
* For comment_sources, use the 7.x-2.1 tag on GitHub openscholar/comment_sources
* For disqus, use the patch from 7.x-2.1 tag on GitHub openscholar/comment_sources
* For fb_social, use the patch from 7.x-2.1 tag on GitHub openscholar/comment_sources