bump topojson

Author: etpinard

package.json

@@ -74,7 +74,7 @@
     "sane-topojson": "^1.2.0",
     "superscript-text": "^1.0.0",
     "tinycolor2": "^1.3.0",
-    "topojson": "^1.6.19"
+    "topojson": "^1.6.20"
   },
   "devDependencies": {
     "brfs": "^1.4.3",