Astropy-healpix

================

- Added new methods ``healpix_to_xyz`` and ``xyz_to_healpix`` to
the high level interface. [153]
- The ``frame`` keyword argument for the high-level ``HEALPix`` class may now
be a frame name, frame instance, or frame class. [156]
- On instantiation, the ``HEALPix`` class checks the ``order`` argument. [162]
- Drop support for Python 3.6, which has passed end-of-life. [166]

================

- Update package infrastructure to follow APE17 guidelines. [142]
- Added new functions ``healpix_to_xyz`` and ``xyz_to_healpix`` to
convert to/from cartesian coordinates. [141]
- Add ``HEALPix.level`` property to the high-level interface.
This is a shortcut for the ``nside_to_level`` function. [147]

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- Update package infrastructure to use ``setup.cfg``. [134]
- Make sure that Numpy is declared as a build-time dependency. [134]
- Update astropy-helpers to v3.2.2. [134]
- Update minimum required Python version to 3.6. [125]
- Add ``HEALPix.from_header``. [127]
- Clean up C code to avoid compilation warnings. [118, 119, 120, 121, 122, 123]
- Fix unit tests on 32-bit architectures. [117]
- Fix compatibility with Numpy 1.16 and later. [116]

================

- Healpix rangesearch cleanup [113]
- Update astropy-helpers to v2.0.8 [112]
- Rewrite core module in C to make ``healpix_to_lonlat`` and
``lonlat_to_healpix`` broadcastable over both pixel index and nside. [110]

==================

- Ensure .c files are included in tar file.

================

- Remove OpenMP from astropy-healpix [108]
- Fix bilinear interpolation of invalid values [106]
- Add uniq to (level, ipix) and inverse function [105]
- compute z more stably; improve on z2dec [101]
- use more stable cos(Dec) term [94]
- Fix get_interp_weights for phi=None case [89]
- Add pix2vec, vec2pix, ang2vec [73]
- Add ``pixel_resolution_to_nside`` function. [31]