Fix Cursor godoc for First(), Next(), and Get().
Fix Cursor godoc for First(), Next(), and Get().

raggi/bolt,ngaut/bolt,mashuai/bolt,jmptrader/bolt,tvmaly/bolt,boltdb/bolt,samanalysis/bolt,sysbot/bolt,pombredanne/bolt-2,jefby/bolt,brahmaroutu/bolt,joyrexus/bolt,yew011/bolt,conseweb/bolt,dindinet/bolt-1,benbjohnson/bolt,btcsuite/bolt,Apsalar/bolt,xuzhaokui/bolt,tv42/bolt,lmars/bolt,linearregression/bolt,wyzssw/bolt,etcd-io/bbolt,cep21/bolt,odeke-em/bolt,pspeter3/bolt,mr-justin/bolt,Shopify/bolt,dajohi/bolt,chlorm-forks/bolt,nilslice/bolt,li-ang/bolt,hvnsweeting/bolt,Compasses/bolt