Remove "before" field from Response

Listing responses only ever contain a non-empty "before" field when the
"count" parameter is provided, which is only useful for the HTML
website, not really needed for API clients

Signed-off-by: Vartan Benohanian <vartanbeno@gmail.com>

reddit/message.go

@@ -42,25 +42,19 @@ type inboxThing struct {
 
 type inboxListing struct {
 	inboxThings
-	after  string
-	before string
+	after string
 }
 
 func (l *inboxListing) After() string {
 	return l.after
 }
 
-func (l *inboxListing) Before() string {
-	return l.before
-}
-
 // UnmarshalJSON implements the json.Unmarshaler interface.
 func (l *inboxListing) UnmarshalJSON(b []byte) error {
 	root := new(struct {
 		Data struct {
 			Things inboxThings `json:"children"`
 			After  string      `json:"after"`
-			Before string      `json:"before"`
 		} `json:"data"`
 	})
 
@@ -71,7 +65,6 @@ func (l *inboxListing) UnmarshalJSON(b []byte) error {
 
 	l.inboxThings = root.Data.Things
 	l.after = root.Data.After
-	l.before = root.Data.Before
 
 	return nil
 }