Style cleanup in gradebook

* don't display thousands of '%' characters
* s/percentage/fraction/, since that's what it is

lms/templates/gradebook.html

@@ -42,19 +42,19 @@
         <th>Total</th>
       </tr>
 
-      <%def name="percent_data(percentage)">
+      <%def name="percent_data(fraction)">
         <%
           letter_grade = 'None'
-          if percentage > 0:
+          if fraction > 0:
             letter_grade = 'F'
             for grade in ['A', 'B', 'C']:
-              if percentage >= course.grade_cutoffs[grade]:
+              if fraction >= course.grade_cutoffs[grade]:
                 letter_grade = grade
                 break
 
           data_class = "grade_" + letter_grade
         %>
-        <td class="${data_class}" data-percent="${percentage}">${ "{0:.0%}".format( percentage ) }</td>
+        <td class="${data_class}" data-percent="${fraction}">${ "{0:.0f}".format( 100 * fraction ) }</td>
       </%def>
 
       %for student in students: