Address further accessibility review notes.

poll/public/handlebars/poll_studio.handlebars

@@ -17,6 +17,9 @@
         {{/if}}
     </div>
     <span class="tip setting-help">
+        You can make limited use of Markdown in answer texts, preferably only bold and italics.
+    </span>
+    <span class="tip setting-help">
         {{#if image}}
         This must have an image URL or text, and can have both.  If you add an image, an alternate text that describes
         the image in a way that would allow someone to answer the poll if the image did not load is strongly encouraged.

poll/public/html/poll.html

@@ -14,7 +14,7 @@
               {% if value.img %}
               <div class="poll-image">
                   <label for="{{url_name}}-answer-{{key}}" class="poll-image-label">
-                      <img src="{{value.img}}" alt="{{value.img_alt}}"/>
+                      <img src="{{value.img}}" alt="{{value.img_alt|default_if_none:''}}"/>
                   </label>
               </div>
               {% endif %}

poll/public/html/survey.html

@@ -18,14 +18,18 @@
                 <td class="survey-question">
                     {% if question.img %}
                         <div class="poll-image-td">
-                            <img src="{{question.img}}" alt="question.img_alt"/>
+                            <img src="{{question.img}}" alt="{{question.img_alt|default_if_none:''}}"/>
                         </div>
                     {% endif %}
                   {{question.label|safe}}
                 </td>
-            {% for answer, answer_details in answers %}
+            {% for answer, label in answers %}
                 <td class="survey-option">
                   <input type="radio" name="{{key}}" value="{{answer}}"{% if question.choice == answer %} checked{% endif %}/>
+                  <label>
+                    <input type="radio" name="{{key}}" value="{{answer}}"{% if question.choice == answer %} checked{% endif %}/>
+                    <span class="sr">{{label}}</span>
+                  </label>
                 </td>
             {% endfor %}
             </tr>