Return the reader object so we can listen for the onloadend event and recheck previously checked radio buttons
Add recheck buttons after downloading new data from server

Only bug is when you try to download data from server that is already
available, because the download_dataset just returns, but not as a
object which support the .done method and so it triggers an error. Just
need to check the object returned from download_dataset and make sure it
is not 'undefined'.

Maybe implement function to hold the checked_input and return
input_array