Make student mastery outcome groups accessible

Fixes CNVS-14008

Test Plan:

1) Create a course and add a student
2) Turn on the Student Mastery Gradebook feature
3) Add at least 2 outcome groups each with at least 2 outcomes
4) Masquerade as the student, and visit the Learning Mastery grades tab
5) Verify with screenreader that outcome groups are clearly clickable

Change-Id: Ib9773d8275c7adb13783ee6b0acac551b59fc09b
Reviewed-on: https://gerrit.instructure.com/37702
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Joel Hough <joel@instructure.com>
QA-Review: Steven Shepherd <sshepherd@instructure.com>
Product-Review: Matthew Wheeler <mwheeler@instructure.com>

Author: mcwqy9

app/coffeescripts/views/grade_summary/GroupView.coffee

@@ -16,6 +16,7 @@ define [
 
     events:
       'click .group-description': 'expand'
+      'keyclick .group-description': 'expand'
 
     template: template
 
@@ -27,7 +28,12 @@ define [
         itemView: OutcomeView
       outcomesView.render()
 
-    expand: -> @$el.toggleClass('expanded')
+    expand: ->
+      @$el.toggleClass('expanded')
+      if @$el.hasClass("expanded")
+        @$el.children("div.group-description").attr("aria-expanded", "true")
+      else
+        @$el.children("div.group-description").attr("aria-expanded", "false")
 
     statusTooltip: ->
       switch @model.status()

app/views/jst/grade_summary/group.handlebars

@@ -1,4 +1,4 @@
-<div class="group-description">
+<div class="group-description" role='button' tabindex='0' aria-controls="group_detail-{{id}}" aria-expanded='false'>
   <div class="outcome-icon {{status}}" data-tooltip title="{{statusTooltip}}" aria-label="Outcome Group: {{title}} status is {{statusTooltip}}">
     {{#if started}}
       {{#ifEqual status 'mastery'}}
@@ -14,10 +14,10 @@
       <i class="icon-empty"></i>
     {{/if}}
   </div>
-  <h3 class="group-title">{{title}}</h3>
+  <h3 class="group-title"><span role='button' tabindex='0'>{{title}}</span></h3>
   <div class="group-status" aria-label="{{mastery_count}} out of {{count}} outcomes mastered">
     <strong>{{mastery_count}}</strong>/{{count}} <span>Outcomes</span>
   </div>
 </div>
-<div class="outcomes">
+<div id="group_detail-{{id}}" class="outcomes">
 </div>