Version 3.0.1

2019 Aug 21

• Remove Astropy version cap; it was intended to promote simultaneous Python 2/3 compatibility, but if someone wants to use the newer version, that's fine too.
• Fix a bug in the Healpix wrapper (#52).
• Fix some lingering Python 2/3 compatibility issues (#51).
• Honor pos_def in the 1D real CLEAN (#44)
• Install the Helmboldt catalog data files, which were mistakenly not being included in installations (#45)
• Rename the package directory in the source tree from aipy_src to aipy.