v4.0.0

Healpix v4.0.0

Diff since v3.0.1

Closed issues:

• [Question] implementation of query disc (#27)
• getting back coordinates(vertices) from equirectangular projection (#77)
• type instability in documentation (#79)

Merged pull requests:

• Update index.md (#71) (@xzackli)
• Update map_pixelfunc.jl (#72) (@xzackli)
• Support NSIDE greater than 8192 (#75) (@ziotom78)
• Use a more robust algorithm for vec2ang (#76) (@ziotom78)
• Add Base.parent to HealpixMap (#78) (@xzackli)
• Implement queryDiscRing and queryStripRing (#80) (@ziotom78)
• Add functions to calculate pixel boundaries (#81) (@ziotom78)
• Various doc fixes (#82) (@ziotom78)