Ctrl+C does not quit the program on multiple ReadLine prompts:

I have 2 ReadLine() questions and when I hit Ctrl+C on any of them, the program is not exiting as expected, but proceeding to the next question.

```
var name, displayName string

sh := ishell.New()
sh.AddCmd(&ishell.Cmd{
Name: "default",
Func: func(c *ishell.Context) {
c.Printf("Name: ")
name = c.ReadLine()

c.Printf("Display name (optional): ")
displayName = c.ReadLine()
}})
sh.Process("default")

fmt.Println("Answers:", name, displayName)
```

Hit Ctrl+c on the first question, falls back to second question:
```
Name: ^C
Display name (optional):
```

hit Ctrl+C on second question, it proceeded on running the rest of the program:

```
Name: ^C
Display name (optional): ^C
Answers:
```

it should be quitting the program on first Ctrl+C.