New d3.geo.transform API. Rather than closures, use `this.stream`. TODO `this.sink`, `this.next`? The new implementation is faster: rather than each method being implemented as a closure, it defines a factory method for creating transform instances.
* d3.geo.gnomonic ↦ d3.geoGnomonic
* d3.geo.mercator ↦ d3.geoMercator
Removed support for the fallback projection pipeline, d3.geoProjection(*function*). Simplified how projection pipelines are cached internally (an undocumented feature of 3.x).
* d3.geo.orthographic ↦ d3.geoOrthographic
* d3.geo.stereographic ↦ d3.geoStereographic
Renamed *circle*.origin ↦ *circle*.center and *circle*.angle ↦ *circle*.radius.