removed new post icon and added font-awesome replacement

lms/static/sass/_discussion.scss

@@ -130,7 +130,6 @@ body.discussion {
       height: 17px;
       margin: 8px 7px 0 0;
       font-size: 16px;
-      padding-right: $baseline/2;
       vertical-align: middle;
       color: $white;
     }

lms/static/sass/course/_discussions-inline.scss

@@ -336,7 +336,6 @@
     height: 17px;
     margin: 8px 7px 0 0;
     font-size: 16px;
-    padding-right: $baseline/2;
     vertical-align: middle;
     color: $white;
   }

lms/templates/discussion/_discussion_course_navigation.html

@@ -3,6 +3,6 @@
 
 <%block name="extratabs">
 % if has_permission(user, 'create_thread', course.id):
-    <li class="right"><a href="#" class="new-post-btn"><span class="icon icon-edit"></span>New Post</a></li>
+    <li class="right"><a href="#" class="new-post-btn"><span class="icon icon-edit new-post-icon"></span>New Post</a></li>
 % endif
 </%block>
\ No newline at end of file