Download: include filename in URL.

This way your browser will save it with a sensible name.
diff --git a/app.py b/app.py
index 006d3d2..0779746 100644
--- a/app.py
+++ b/app.py
@@ -277,7 +277,7 @@
 wsgi_app = webapp2.WSGIApplication([
     (r'/', MainHandler),
     (r'/upload', UploadHandler),
-    (r'/download/([^/]+)$', DownloadHandler),
+    (r'/download/([^/]+)/[^/]+$', DownloadHandler),
     (r'/view/([^/]+)$', ViewHandler),
     (r'/save/([^/]+)$', SaveHandler),
     (r'/json/([^/]+)$', JsonHandler),
diff --git a/view.html b/view.html
index b15fdca..987cd59 100644
--- a/view.html
+++ b/view.html
@@ -3,7 +3,8 @@
 {% block body %}
   <a href='/'>&larr; Index</a><p>
  
-  Filename: <a href="/download/{{blob.key()}}">{{blob.filename}}</a><br>
+  Filename: <a href="/download/{{blob.key()}}/{{blob.filename}}"
+    >{{blob.filename}}</a><br>
   Uploaded by: {{obj.create_user_email}} at {{obj.create_time}}<br>
   Size: {{'%.2f' % (blob.size/1e6)}} Mbytes<p>