Fix markdown bug multiple multiplechoice

This bug affects the case of more than one multiplechoice
all in one problem.
Also adding a test case for this form.

common/lib/xmodule/xmodule/js/spec/problem/edit_spec.coffee

@@ -287,6 +287,62 @@ describe 'MarkdownEditingDescriptor', ->
         </div>
         </solution>
         </problem>""")
+
+    it 'converts a series of multiplechoice to xml', ->
+      data = MarkdownEditingDescriptor.markdownToXml("""bleh
+        (!x) a
+        () b
+        () c
+        yatta
+        ( ) x
+        ( ) y
+        (x) z
+        testa
+        (!) i
+        ( ) ii
+        (x) iii
+        [Explanation]
+        When the student is ready, the explanation appears.
+        [Explanation]
+        """)
+      expect(data).toEqual("""<problem>
+        <p>bleh</p>
+        <multiplechoiceresponse>
+          <choicegroup type="MultipleChoice" shuffle="true">
+            <choice correct="true">a</choice>
+            <choice correct="false">b</choice>
+            <choice correct="false">c</choice>
+          </choicegroup>
+        </multiplechoiceresponse>
+        
+        <p>yatta</p>
+        <multiplechoiceresponse>
+          <choicegroup type="MultipleChoice">
+            <choice correct="false">x</choice>
+            <choice correct="false">y</choice>
+            <choice correct="true">z</choice>
+          </choicegroup>
+        </multiplechoiceresponse>
+        
+        <p>testa</p>
+        <multiplechoiceresponse>
+          <choicegroup type="MultipleChoice" shuffle="true">
+            <choice correct="false">i</choice>
+            <choice correct="false">ii</choice>
+            <choice correct="true">iii</choice>
+          </choicegroup>
+        </multiplechoiceresponse>
+        
+        <solution>
+        <div class="detailed-solution">
+        <p>Explanation</p>
+        
+        <p>When the student is ready, the explanation appears.</p>
+        
+        </div>
+        </solution>
+        </problem>""")
+
     it 'converts OptionResponse to xml', ->
       data = MarkdownEditingDescriptor.markdownToXml("""OptionResponse gives a limited set of options for students to respond with, and presents those options in a format that encourages them to search for a specific answer rather than being immediately presented with options from which to recognize the correct answer.
 

common/lib/xmodule/xmodule/js/src/problem/edit.coffee

@@ -195,9 +195,9 @@ class @MarkdownEditingDescriptor extends XModule.Descriptor
       xml = xml.replace(/\n^\=\=+$/gm, '');
 
       // group multiple choice answers
+      xml = xml.replace(/(^\s*\(.{0,3}\).*?$\n*)+/gm, function(match, p) {
         var choices = '';
         var shuffle = false;
-      xml = xml.replace(/(^\s*\(.{0,3}\).*?$\n*)+/gm, function(match, p) {
         var options = match.split('\n');
         for(var i = 0; i < options.length; i++) {
           if(options[i].length > 0) {