Furuti 3 - projection.clipPolygon()

Forked from Fil's gist and made it minimalist:

• removed all but sphere
• filled sphere to give a visual clue when it is "interruped"

Fil's gist is about:

• Research for d3-geo-projection/pull/86 and d3-geo/issues/46.
• Re-incorporating Jason Davies’ clipPolygon() code into d3v4.
• Code base at Fil/d3-geo:clip-polygon.
• See also https://bl.ocks.org/Fil/694ba0d0bc1fc4c24eb257dc210eb01a