tentative UI and styling changes to support images

.bundle/config

+---
+BUNDLE_BIN: bin

common/static/common/templates/discussion/response-comment-show.underscore

 <div class="discussion-comment" id="comment_<%- id %>">
+  <div class="author-image level-comment">
+    <img class="image-frame" src="https://d37djvu3ytnwxt.cloudfront.net/static/images/edx-theme/default-profile_120.41d2f8cbbbbd.png" alt="Profile image for post author">
+  </div>
   <div class="response-body"><%- body %></div>
   <%=
       _.template(

common/static/common/templates/discussion/thread-response-show.underscore

 <header class="wrapper-response-header">
+  <div class="author-image level-response">
+    <img class="image-frame" src="https://d37djvu3ytnwxt.cloudfront.net/static/images/edx-theme/default-profile_120.41d2f8cbbbbd.png" alt="Profile image for post author">
+  </div>
   <div class="response-header-content">
     <%= author_display %>
     <p class="posted-details">

common/static/common/templates/discussion/thread-show.underscore

 <div class="discussion-post">
     <header class="wrapper-post-header">
+        <div class="author-image level-post">
+            <img class="image-frame" src="https://d37djvu3ytnwxt.cloudfront.net/static/images/edx-theme/default-profile_120.41d2f8cbbbbd.png" alt="Profile image for post author">
+        </div>
         <div class="post-header-content">
             <h1 class="post-title"><%- title %></h1>
             <p class="posted-details">

lms/static/sass/discussion/views/_thread.scss

@@ -25,7 +25,7 @@ body.discussion, .discussion-module {
 
     .post-header-content {
       display: inline-block;
-      width: flex-grid(9,12);
+      width: flex-grid(8,12); 
     }
 
     .post-header-actions {
@@ -45,7 +45,7 @@ body.discussion, .discussion-module {
     .response-header-content {
       display: inline-block;
       vertical-align: top;
-      width: flex-grid(11,12);
+      width: flex-grid(10,12);
     }
 
     .response-header-actions {