add cancel button for new post

lms/static/coffee/src/discussion/discussion.coffee

@@ -54,12 +54,10 @@ initializeFollowDiscussion = (discussion) ->
           Discussion.setContentInfo response.content['id'], 'editable', true
           Discussion.initializeContent($thread)
           Discussion.bindContentEvents($thread)
-          $(".new-post-form").hide()
-          $local(".discussion-new-post").show()
+          $(".new-post-form").addClass("collapsed")
 
     handleCancelNewPost = (elem) ->
-      $local(".new-post-form").hide()
-      $local(".discussion-new-post").show()
+      $(".new-post-form").addClass("collapsed")
 
     handleSimilarPost = (elem) ->
       $title = $local(".new-post-title")

lms/static/coffee/src/discussion/templates.coffee

@@ -18,7 +18,8 @@ Discussion = @Discussion
         <input type="checkbox" class="discussion-auto-watch" id="discussion-autowatch-${discussion_id}" checked="">
         <label for="discussion-auto-watch-${discussion_id}">follow this thread</label>
       </div>
-      <div class="reply-post-control">        
+      <div class="new-post-control post-control">        
+        <a class="discussion-cancel-post" href="javascript:void(0)">Cancel</a>
         <a class="discussion-submit-post control-button" href="javascript:void(0)">Submit</a>
       </div>
     </form>

lms/static/sass/_discussion.scss

@@ -656,8 +656,8 @@ $tag-text-color: #5b614f;
         height: 0;
       }
 
-      .reply-post-control {
-        height: 0;
+      .post-control {
+        display: none;
       }
 
       .tagsinput {
@@ -666,7 +666,7 @@ $tag-text-color: #5b614f;
     }
 
     .new-post-control {
-      margin-left: 80%;
+      margin-left: 75%;
       margin-top: 1%;
     }
 
@@ -775,7 +775,7 @@ $tag-text-color: #5b614f;
         }
       }
 
-      .reply-post-control {
+      .post-control {
         overflow: hidden;
       }
     }