Don't require -u flag for writeas auth

Instead of writeas auth -u <username>, now you can just use
writeas auth <username>

cmd/writeas/cli.go

@@ -239,11 +239,6 @@ func main() {
 					Usage: "Use a different port to connect to Tor",
 					Value: 9150,
 				},
-				cli.StringFlag{
-					Name:  "u",
-					Usage: "Username for authentication",
-					Value: "",
-				},
 			},
 		},
 		{

cmd/writeas/commands.go

@@ -214,9 +214,9 @@ func cmdAuth(c *cli.Context) error {
 	}
 
 	// Validate arguments and get password
-	username := c.String("u")
+	username := c.Args().Get(0)
 	if username == "" {
-		return cli.NewExitError("usage: writeas auth -u <username>", 1)
+		return cli.NewExitError("usage: writeas auth <username>", 1)
 	}
 
 	fmt.Print("Password: ")