title: Header Title not centered in React Native using native-base
body: <p>I'm using native-base to create a React Native app:</p>
  
  <p>I'm using the Header Component to display Body, Left and Right elements. According to the docs, the title should automatically center but it does not (as seen below).</p>
  
  <p>Am I missing something simple here? Any help would be appreciated!</p>
  
  <pre><code>import { 
      Container,
      Header,
      Content,
      Left,
      Right,
      Body,
      Title,
      Icon
  } from "native-base"
  
  export default class Seminars extends React.Component{
  
      render(){
          return(
              &lt;Container style={styles.container}&gt;
                  &lt;Header style={styles.header}&gt;
                      &lt;Left&gt;
                          &lt;Icon name='arrow-back' /&gt;
                      &lt;/Left&gt;
                      &lt;Body&gt;
                          &lt;Title&gt;Seminars&lt;/Title&gt;
                      &lt;/Body&gt;
                      &lt;Right&gt;
                          &lt;Icon name='menu' /&gt;
                      &lt;/Right&gt;
                  &lt;/Header&gt;
                  &lt;Content contentContainerStyle={styles.content} &gt;
                      &lt;Text&gt;Content Here&lt;/Text&gt;
                  &lt;/Content&gt;
              &lt;/Container&gt;
          )
      }
  }
  const styles = StyleSheet.create({
      container: {
  
      },
      header: {
          paddingRight: 15,
          paddingLeft: 15
      },
      content: {
          display: "flex",
          flex: 1,
          justifyContent: "center",
          padding: 15
      }
  });
  </code></pre>
  
  <p><a href="https://i.stack.imgur.com/5qEcE.png" rel="noreferrer"><img src="https://i.stack.imgur.com/5qEcE.png" alt="enter image description here"></a></p>