Fix a few topology.filter bugs and reverse holes.
Fix a few topology.filter bugs and reverse holes.

* Counterclockwise ring areas were being incorrectly calculated (the
  area A is already negative so the positive area is π + A).
* The MultiPolygon filter should *exclude* polygons with an area smaller
  than the minimum.

maxogden/topojson,studiowangfei/topojson,koshlan/topojson,ststeiger/topojson,AlpinHologramm/topojson,mbostock/topojson,btahir/topojson,tsl3su/WorldMap_Choropleth,whoinlee/topojson,ongerit/topojson,hcxiong/topojson,lyhpcha/topojson,youprofit/topojson