ratio for calculation of bbox area should always be > 1 (uber#708)

src/h3lib/lib/bbox.c

@@ -121,9 +121,14 @@ H3Error bboxHexEstimate(const BBox *bbox, int res, int64_t *out) {
     p2.lat = bbox->south;
     p2.lng = bbox->west;
     double d = H3_EXPORT(greatCircleDistanceKm)(&p1, &p2);
+    double diffLng = fabs(p1.lng - p2.lng);
+    double diffLat = fabs(p1.lat - p2.lat);
+    double length = fmax(diffLng, diffLat);
+    double width = fmin(diffLng, diffLat);
+    double ratio = length / width;
     // Derived constant based on: https://math.stackexchange.com/a/1921940
     // Clamped to 3 as higher values tend to rapidly drag the estimate to zero.
-    double a = d * d / fmin(3.0, fabs((p1.lng - p2.lng) / (p1.lat - p2.lat)));
+    double a = d * d / fmin(3.0, ratio); 
 
     // Divide the two to get an estimate of the number of hexagons needed
     double estimateDouble = ceil(a / pentagonAreaKm2);