Add Coveralls and issue count in readme.
Add Coveralls and issue count in readme.

YoukaiCat/imgbrd-grabber,Bionus/imgbrd-grabber,Bionus/imgbrd-grabber,Bionus/imgbrd-grabber,YoukaiCat/imgbrd-grabber,Bionus/imgbrd-grabber,Bionus/imgbrd-grabber,Bionus/imgbrd-grabber