Clean up lint in various packages

Changes fall into one of the following:

- gofmt -s
- receiver name is inconsistent
- omit unused 2nd value from range
- godoc comment formed incorrectly
- err assigned and not used
- if block ends with a return statement followed by else

related/inverted_index.go

@@ -418,7 +418,7 @@ func DecodeConfig(in interface{}) (Config, error) {
 	}
 
 	if c.ToLower {
-		for i, _ := range c.Indices {
+		for i := range c.Indices {
 			c.Indices[i].ToLower = true
 		}
 	}