update image & header explanation

Author: kyleturco

docs/app/Examples/elements/Header/Content/HeaderImageExample.js

@@ -4,7 +4,7 @@ import {Header, Image} from 'stardust';
 
 export default class HeaderImageExample extends Component {
   render() {
-    const photo = <Image className='circular' src={faker.image.city()} />;
+    const photo = <Image className='circular' src={faker.image.city(120, 120)} />;
     return (
       <Header.H2 image={photo}>
         Welcome to Our City!

docs/app/Examples/elements/Header/HeaderExamples.js

@@ -10,9 +10,10 @@ export default class HeaderExamples extends Component {
     return (
       <div>
         <Message className='warning'>
-          Semantic UI uses conventional h1, h2, etc... for headers. For cleanliness in Stardust,
-          we've created a Header component that uses sub-components for specifying header clasess.
-          For example, a h2 tag will written as Header.H2. See the examples below for further clarfication.
+          Semantic UI uses both <code>&lt;div&gt;</code> and <code>&lt;h*&gt;</code> tags
+          for headers. In Stardust, the <code>&lt;Header&gt;</code> component renders a
+          <code>&lt;div&gt;</code>. While subcomponents, <code>&lt;Header.H*&gt;</code>,
+          render an <code>&lt;h*&gt;</code>. See the examples below for further clarfication.
         </Message>
         <HeaderTypesExamples />
         <HeaderContentExamples />