fix javascript mime-type in HTML exporter

It's application/javascript, not text/javascript.
The result was javascript output never showing up in nbconvert.

IPython/nbconvert/exporters/html.py

@@ -37,7 +37,7 b' class HTMLExporter(TemplateExporter):'
     def default_config(self):
         c = Config({
             'NbConvertBase': {
-                'display_data_priority' : ['text/javascript', 'text/html', 'text/markdown', 'application/pdf', 'image/svg+xml', 'text/latex', 'image/png', 'image/jpeg', 'text/plain']
+                'display_data_priority' : ['application/javascript', 'text/html', 'text/markdown', 'application/pdf', 'image/svg+xml', 'text/latex', 'image/png', 'image/jpeg', 'text/plain']
                 },
             'CSSHTMLHeaderPreprocessor':{
                 'enabled':True

IPython/nbconvert/templates/html/basic.tpl

@@ -192,7 +192,7 b" height={{output.metadata['image/jpeg']['height']}}"
 {%- block data_javascript scoped %}
 <div class="output_subarea output_javascript {{extra_class}}">
 <script type="text/javascript">
-{{ output.data['text/javascript'] }}
+{{ output.data['application/javascript'] }}
 </script>
 </div>
 {%- endblock -%}