Don't map the .jsonp extension to the JS MIME type

Remove `.jsonp` as there isn't any convention around the JSONP MIME-type
or the `.jsonp` extension. Also, it seems that, `application/javascript`
is arguably the wrong type to use for JSONP.

Ref: broofa/node-mime#64

mime.types

@@ -20,7 +20,7 @@ types {
   image/x-jng                           jng;
 
 # JavaScript
-  application/javascript                js jsonp;
+  application/javascript                js;
   application/json                      json;
 
 # Manifest files