sheetify@5.1.0 breaks build 🚨 (#238)

* chore(package): update sheetify to version 5.1.0

https://greenkeeper.io/

* deps: upgrade insert-css to 1.0.0

package.json

@@ -58,7 +58,7 @@
     "es2020": "^1.0.1",
     "geval": "~2.1.1",
     "gzip-size-cli": "^1.0.0",
-    "insert-css": "^0.2.0",
+    "insert-css": "^1.0.0",
     "istanbul": "^0.4.4",
     "min-document": "~2.18.0",
     "pretty-bytes-cli": "^2.0.0",
@@ -66,7 +66,7 @@
     "proxyquire-universal": "~1.0.8",
     "proxyquireify": "~3.2.0",
     "server-router": "^3.0.0",
-    "sheetify": "^5.0.0",
+    "sheetify": "^5.1.0",
     "standard": "^8.0.0",
     "tachyons": "^4.0.0-beta.19",
     "tape": "^4.5.1",