Added contribution request to README
Added contribution request to README

PebbleTemplates/pebble,samlanning/pebble,ebussieres/pebble,DanStout/pebble,chambas/pebble,jcarvalho/pebble,PebbleTemplates/pebble,dotneet/pebble,hectorlf/pebble,mbosecke/pebble