Add Airy’s minimum-error azimuthal projection.
Update README.md
Fix typo.
Add Chamberlin trimetric.
Add another Airy link.
Update README.md
Update README.md
Update README.md
Add inverse for d3.geo.interrupt.

This assumes non-overlapping bounding boxes for lobes.
Simplify slightly.
Add Gilbert’s Two-World Perspective.
Add tests for gilbert.
Update D3 dependency version.

Version 3.1.x is required as d3.geo.chamberlin uses d3.geo.rotation.
Simplify two-point equidistant.
Add link to Gilbert’s Two-World example.
Add thumbnail for gilbert.
Update dependencies.
Fix d3.geo.gilbert.{translate,scale,rotate}.
Rewrite d3.geo.gilbert.

It is impossible to make this a useful d3.geo.projection instance, since
rotation needs to be applied after Gilbert’s conformal transformation on
the sphere, but before the final orthographic projection.  As
d3.geo.projection takes care of rotation for us, as well as automatic
centring, it is simpler and more useful to allow wrapping of any target
projection.
Add note about d3.geo.gilbert.