Numerical response now works and round tripping works.

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

@@ -135,6 +135,9 @@ class @MarkdownEditingDescriptor extends XModule.Descriptor
 
       // rid white space
       xml = xml.replace(/\n\n\n/g, '\n');
+      
+      // surround w/ problem tag
+      xml = '<problem>\n' + xml + '\n</problem>';
 
       return xml;
     }

common/lib/xmodule/xmodule/templates/problem/numericalresponse.yaml

@@ -3,7 +3,8 @@ metadata:
     display_name: Numerical Response
     rerandomize: never
     showanswer: always
-    markdown: "A numerical response problem accepts a line of text input from the
+    markdown: |
+       A numerical response problem accepts a line of text input from the
        student, and evaluates the input for correctness based on its
        numerical value.  
 
@@ -18,7 +19,6 @@ metadata:
     
        Enter the number of fingers on a human hand: 
        = 5
-        "
 data: |
    <problem>
    <p>