Add inverse azimuthal equal-area projection.
Add inverse azimuthal equal-area projection.

Also, Hammer is in fact a modified azimuthal equal-area, so this code is
reused.

fmacias64/d3-plugins,shilon5/d3-more-plugins,fmacias64/d3-plugins,deldersveld/d3-plugins,sidhart/d3-plugins,deldersveld/d3-plugins,HunjaeJung/d3-plugins,johnochs/d3-plugins,kaktus40/d3-plugins,gronke/d3-plugins,gweinert/d3-plugins,larskotthoff/d3-plugins,HunjaeJung/d3-plugins,johnochs/d3-plugins,larskotthoff/d3-plugins,sidhart/d3-plugins,ddrugg/d3-plugins,shilon5/d3-more-plugins,gronke/d3-plugins,d3/d3-plugins,gweinert/d3-plugins,grepman/d3-plugins,emeeks/d3-plugins,yinchanted/d3-plugins,emeeks/d3-plugins,d3/d3-plugins,kaktus40/d3-plugins,ddrugg/d3-plugins,yinchanted/d3-plugins,grepman/d3-plugins