修改TextInput 默认文案 review by hongmo

@@ -300,7 +300,7 @@ export default class Detail extends Component {
                     <View style={styles.commtentBottomView}>
                         <TextInput
                                style={styles.inputStyle}
-                               placeholder = {this.state.relayToUsername == '' ? '你好，' : '回复:' + this.state.relayToUsername}
+                               placeholder = {this.state.relayToUsername == '' ? '赶紧参与评论吧~' : '回复:' + this.state.relayToUsername}
                                returnKeyType = 'send'
                                enablesReturnKeyAutomatically = {true}
                                onSubmitEditing = {this._onSubmitEditing}