PyPi packaging issues

First of all, I really appreciate how easy it is to plot healpix data with the package!

I'm working on the ESiWACE3 project and came across the following issues with pyicon's packaging:

• The sdist on PyPi is missing the requirements.txt file, so one cannot build the package from source
• The code has several imports from ipdb, which is only useful for debugging. These imports should ideally be commented out in release versions or check if ipdb is available
• pyicon should not have pytest and ipdb as dependencies, since they’re for testing only (and requiring users to install them doesn’t make sense). Perhaps they could be moved into an optional (dev) dependency.

Thanks for your help!