hourly_timeseries.py output_path argument should be output_dir

[mhidas]

From @mphemming:

Thought this might be a good place to mention that I ran into an error when creating hourly timeseries products locally. Using the latest code on Github, I had to change output_dir=args.output_path on line 579 in 'hourly_timeseries.py' to output_dir=args.output_dir for the code to work. Easy fix but worth mentioning.

[mhidas]

There's an open PR to standardise and simplify these command-line arguments: #120 , which now includes the necessary fix above.

@mphemming feel free to take a look and let us know if the code on that branch works for you.