Rename NextResult -> NextPath

See discussion in #92.

graph/memstore/iterator.go

@@ -111,7 +111,7 @@ func (it *Iterator) Result() graph.Value {
 	return it.result
 }
 
-func (it *Iterator) NextResult() bool {
+func (it *Iterator) NextPath() bool {
 	return false
 }
 

graph/memstore/triplestore_test.go

@@ -128,7 +128,7 @@ func TestIteratorsAndNextResultOrderA(t *testing.T) {
 	)
 	for {
 		got = append(got, ts.NameOf(all.Result()))
-		if !outerAnd.NextResult() {
+		if !outerAnd.NextPath() {
 			break
 		}
 	}