Replace UITextView with UITextField & add prompt.

This is my first pull, oh...> <

1.Replace the class member UITextView *textView into THContactTextField *textView. THContactTextField is a subclass of the UITextField, which detects the delete action when the length of the text of textView (textfield, whatever) equals to 0.

2.Add a prompt for my own thing..It's easy to modify, thanks.

![ios 2014513 7 49 24](https://cloud.githubusercontent.com/assets/985230/2957294/579409f8-da9d-11e3-9633-9050afc8264b.png)