chore(package): update aegir to version 20.0.0

Author: greenkeeper[bot]

package.json

@@ -80,7 +80,7 @@
     "through2": "^3.0.1"
   },
   "devDependencies": {
-    "aegir": "^19.0.3",
+    "aegir": "^20.0.0",
     "browser-process-platform": "~0.1.1",
     "chai": "^4.2.0",
     "cross-env": "^5.2.0",