chore(navigation): include protocol in external links

Author: skipjack

src/components/Navigation/Navigation.jsx

@@ -30,13 +30,13 @@ export default class Navigation extends React.Component {
           ...links,
           {
             title: 'GitHub Repository',
-            url: '//github.com/webpack/webpack',
+            url: 'https://github.com/webpack/webpack',
             className: 'navigation__item--icon',
             content: <i className="icon-github" />
           },
           {
             title: 'Webpack on Stack Overflow',
-            url: '//stackoverflow.com/questions/tagged/webpack',
+            url: 'https://stackoverflow.com/questions/tagged/webpack',
             className: 'navigation__item--icon',
             content: <i className="icon-stack-overflow" />
           },

src/components/Site/Site.jsx

@@ -71,7 +71,7 @@ class Site extends React.Component {
             },
             { content: 'Contribute', url: '/contribute' },
             { content: 'Vote', url: '/vote' },
-            { content: 'Blog', url: '//medium.com/webpack' }
+            { content: 'Blog', url: 'https://medium.com/webpack' }
           ]} />
 
         { window.document !== undefined ? (