解决代码冲突。code review by 于良

@@ -64,7 +64,6 @@ let styles = StyleSheet.create({
         width: 45,
         height: 45,
         justifyContent: 'center',
-        alignItems: 'center',
     },
     avatarContainer: {
         width: 44,

@@ -168,7 +168,6 @@ export default class Posting extends Component {
                 >
                     <TextInput
                         style={styles.contentInput}
-                        placeholder='#b0b0b0'
                         placeholder='用力敲出你想说的...'
                         maxLength={2000}
                         multiline={true}