Set og:image meta for seo by default on all pages

This adds a larger, wide format version of the elixir log as the
og:image and twitter:image seo meta tags for all pages.

Author: sorentwo

Diff for: _config.yml

@@ -22,7 +22,14 @@ plugins:
 defaults:
   - scope:
       path: ""
+      type: pages
+    values:
+      layout: default
+      image: /images/social/elixir-og-card.jpg
+  - scope:
+      path: "posts"
       type: posts
     values:
       layout: post
       permalink: /blog/:year/:month/:day/:title/
+      image: /images/social/elixir-og-card.jpg

Diff for: cases.html

@@ -1,6 +1,5 @@
 ---
 section: cases
-layout: default
 ---
 
 <h1>Cases</h1>

Diff for: images/social/elixir-og-card.jpg

@@ -1,6 +1,5 @@
 ---
 section: home
-layout: default
 ---
 
 <div class="hfeed">