Raise Exception if HTTP status code is not 200

If download request fails raise an exception so
it gets passed back to the user.
Reorder JQuery and Boostrap includes
Delay prompting user for algorithm until file is downloaded

With ESGF we want to prompt the user when the file download
is complete.
If no value is provided store ""
Merge remote-tracking branch 'origin/136-fix-esgf' into next

* origin/136-fix-esgf:
  If no value is provided store ""
  Delay prompting user for algorithm until file is downloaded
  Reorder JQuery and Boostrap includes
  Raise Exception if HTTP status code is not 200