Make staff problem histogram work again

static/coffee/spec/calculator_spec.js

@@ -66,7 +66,7 @@
         return this.calculator.calculate();
       });
       it('send data to /calculate', function() {
-        return expect($.getJSON).toHaveBeenCalledWith('/calculate', {
+        return expect($.getWithPrefix).toHaveBeenCalledWith('/calculate', {
           equation: '1+2'
         }, jasmine.any(Function));
       });

static/coffee/spec/feedback_form_spec.js

@@ -18,7 +18,7 @@
         $('#feedback_subject').val('Awesome!');
         $('#feedback_message').val('This site is really good.');
         $('#feedback_button').click();
-        return expect($.post).toHaveBeenCalledWith('/send_feedback', {
+        return expect($.postWithPrefix).toHaveBeenCalledWith('/send_feedback', {
           subject: 'Awesome!',
           message: 'This site is really good.',
           url: window.location.href

static/coffee/src/courseware.coffee

@@ -22,3 +22,7 @@ class @Courseware
     $('.course-content .problems-wrapper').each ->
       id = $(this).attr('id').replace(/problem_/, '')
       new Problem id, $(this).data('url')
+    $('.course-content .histogram').each ->
+      id = $(this).attr('id').replace(/histogram_/, '')
+      new Histogram id, $(this).data('histogram')
+