pass explicit submission_type for assignment quick add

turns out, according to the mozilla spec, some browsers will fall back
to the text of an option if the value is not specified.  so just to be
clear, we'll explicitly specify 'none' as our submission type for
assignment quick add

fixes CNVS-16548

test plan:
- in IE10, go to the assignment index page
- if an assignment group doesn't already exist, create one
- click the '+' icon to add an assignment to that group
- leave type specified as "Assignment"
- hit save
- it should work
- also make sure other types still work

Change-Id: I06b810a4824535066962c2f915f6edd4c1ea9f56
Reviewed-on: https://gerrit.instructure.com/48838
Tested-by: Jenkins
Reviewed-by: Benjamin Porter <bporter@instructure.com>
QA-Review: Adam Stone <astone@instructure.com>
Product-Review: Simon Williams <simon@instructure.com>

Author: simonista

app/views/jst/assignments/CreateAssignment.handlebars

@@ -8,7 +8,7 @@
       </label>
       <div class="controls">
         <select type="text" id="{{uniqLabel}}_assignment_type" name="submission_types">
-          <option value>{{#t "assignment"}}Assignment{{/t}}</option>
+          <option value="none">{{#t "assignment"}}Assignment{{/t}}</option>
           <option value="discussion_topic">{{#t "discussion_type"}}Discussion{{/t}}</option>
           <option value="online_quiz">{{#t "quiz_type"}}Quiz{{/t}}</option>
           <option value="external_tool">{{#t "external_tool_type"}}External Tool{{/t}}</option>

spec/coffeescripts/views/assignments/CreateAssignmentViewSpec.coffee

@@ -234,3 +234,8 @@ define [
     errors = view.validateBeforeSave(data, [])
     ok errors["points_possible"]
     equal errors['points_possible'][0]['message'], 'Points possible must be a number'
+
+  test 'passes explicit submission_type for Assignment option', ->
+    view = createView(@group)
+    data = view.getFormData()
+    equal data.submission_types, 'none'