Add ability to list feeds of a category.

By providing a category id after the feeds command, list the feeds in that category.

main.go

@@ -13,6 +13,7 @@ import (
 // Help message
 const HELP = `examples:
     mfeed create {category_id} {feed_url}
+    mfeed feeds {category_id}
 
 usage: mfeed [-h] {feeds,categories,create} ...
     feeds       list all the feeds you have
@@ -92,8 +93,9 @@ func main() {
 	return
 }
 
-// Print out all your feeds and their id's
+// Print out all your feeds and their id's, or feeds in a category if provided
 func feeds(client *miniflux.Client) {
+	if len(os.Args) < 3 {
 		feeds, err := client.Feeds()
 		if err != nil {
 			fmt.Println(err)
@@ -102,6 +104,20 @@ func feeds(client *miniflux.Client) {
 		for _, feed := range feeds {
 			fmt.Printf("%d\t%s\n", feed.ID, feed.Title)
 		}
+		return
+	} else if len(os.Args) > 3 {
+		fmt.Println("Too many arguments provided!")
+		return
+	} else {
+		category, err := strconv.Atoi(os.Args[2])
+		if err != nil {
+			panic(err)
+		}
+		feeds, err := client.CategoryFeeds(int64(category))
+		for _, feed := range feeds {
+			fmt.Printf("%d\t%s\n", feed.ID, feed.Title)
+		}
+	}
 }
 
 // Print out all your categories and their id's