Run golint and go vet (#276)

Cleanup the errors and removed deadcode along the way. The leaves
some error laying around, mostly about commenting exported identifier.
We should look hard if those really are needed.

middleware/file/reload_test.go

@@ -39,7 +39,7 @@ func TestZoneReload(t *testing.T) {
 		t.Fatalf("expected 5 RRs, got %d", len(z.All()))
 	}
 	if err := ioutil.WriteFile(fileName, []byte(reloadZone2Test), 0644); err != nil {
-		t.Fatalf("failed to write new zone data", err)
+		t.Fatalf("failed to write new zone data: %s", err)
 	}
 	// Could still be racy, but we need to wait a bit for the event to be seen
 	time.Sleep(1 * time.Second)

middleware/file/secondary.go

@@ -176,7 +176,6 @@ Restart:
 			}
 		}
 	}
-	return nil
 }
 
 // The maximum difference between two serial numbers. If the difference between

middleware/file/tree/less.go

@@ -39,7 +39,6 @@ func less(a, b string) int {
 		i++
 		aj, bj = ai, bi
 	}
-	return 0
 }
 
 func doDDD(b []byte) {