Open graph images and style fixes

Author: benfrancis

css/home.css

@@ -52,7 +52,7 @@
 #framework-section {
   width: 50%;
   box-sizing: border-box;
-  background-color: #4a4a4f;
+  background-color: #4a4a4a;
   float: left;
   text-align: center;
   color: #fff;

framework/images/webthings_framework_banner.png

@@ -18,7 +18,7 @@
   <meta property="og:description" content="Build your own web things" />
   <meta property="og:type" content="website" />
   <meta property="og:url" content="https://webthings.io/framework" />
-  <meta property="og:image" content="https://webthings.io/images/banner.png" />
+  <meta property="og:image" content="https://webthings.io/framework/images/webthings_framework_banner.png" />
   <script src="/js/site.js"></script>
   <script src="js/prism.js"></script>
   <script src="js/tabs.js"></script>

framework/images/webthings_framework_wordmark.svg

@@ -17,7 +17,7 @@
   <meta property="og:description" content="Build your own Web of Things gateway" />
   <meta property="og:type" content="website" />
   <meta property="og:url" content="https://webthings.io/gateway" />
-  <meta property="og:image" content="https://webthings.io/images/banner.png" />
+  <meta property="og:image" content="https://webthings.io/gateway/images/webthings_gateway_banner.png" />
   <script src="/js/site.js"></script>
   <script src="js/carousel.js"></script>
 </head>