Remove the links around figures in the JOSS paper

[leouieda]

Include the links in the figure caption instead to avoid issues when compiling the paper PDF.

You can preview the compiled paper at: http://res.cloudinary.com/hju22ue2k/image/upload/v1580414535/wvsuqwnyi5rgshtoru7i.pdf

The "Figure 1" etc are added automatically when compiling the paper. I used the link to the master branch notebook but this is probably not ideal since that link will break if the notebooks are moved. It would be best to link to the specific version used in the JOSS paper (feel free to update this branch).

openjournals/joss-reviews#1882

1. You have run tests on this submission, either by using Travis Continuous Integration testing testing or running nosetests on your changes?
2. This pull request is directed to the pysal/dev branch.
3. This pull introduces new functionality covered by
   docstrings and
   unittests?
4. You have assigned a
   reviewer and added relevant labels
5. The justification for this PR is:

[leouieda]

@slumnitz any updates on this?

[jGaboardi]

@leouieda I think she is still experiencing issues with a reliable internet connection.

[leouieda]

@jGaboardi thank you for the update. I was mostly checking in on the progress. We're done with the review and this is mostly the only thing left for the paper to be accepted. No rush, though. Let me know this is ready to move forward.

[ljwolf]

This should be very easy to address. I will try to complete it this week

[ljwolf]

Thanks @leouieda! This looks complete to me.