Update usage.rst
Update usage.rst

Fix link usage in docs
fanhero/thumbor,thumbor/thumbor,kkopachev/thumbor,davduran/thumbor,davduran/thumbor,thumbor/thumbor,thumbor/thumbor,kkopachev/thumbor,marcelometal/thumbor,thumbor/thumbor,voxmedia/thumbor,scorphus/thumbor,marcelometal/thumbor,kkopachev/thumbor,fanhero/thumbor,okor/thumbor,gi11es/thumbor,scorphus/thumbor,okor/thumbor,scorphus/thumbor,Bladrak/thumbor,davduran/thumbor,voxmedia/thumbor,scorphus/thumbor,gi11es/thumbor,Bladrak/thumbor,fanhero/thumbor,kkopachev/thumbor,marcelometal/thumbor,okor/thumbor,gi11es/thumbor,davduran/thumbor,fanhero/thumbor,voxmedia/thumbor