Possible bug in filling ghost cell in stegoton_1d example

[cpraveen]

It looks like when filling ghost values, this loop

https://github.com/clawpack/pyclaw/blob/master/examples/stegoton_1d/stegoton.py#L81

should be like this

        for ibc in range(num_ghost):

[ketch]

I think you're right. If you'd like to submit a patch, that would be great.