Update to esm 3.0.28 (#234)

* fix(package): update esm to version 3.0.28

Closes #216

* chore(package): update lockfile

https://npm.im/greenkeeper-lockfile

package-lock.json

@@ -3349,9 +3349,9 @@
       "dev": true
     },
     "esm": {
-      "version": "3.0.26",
-      "resolved": "https://registry.npmjs.org/esm/-/esm-3.0.26.tgz",
-      "integrity": "sha512-AgtiHp4RZLtjnCGahgglLyRtha9SippxmO6JI8MCwJPpslzJqOANmNBI33u7v6znU4abVhhY0qb4v0OTBi2ykA=="
+      "version": "3.0.28",
+      "resolved": "https://registry.npmjs.org/esm/-/esm-3.0.28.tgz",
+      "integrity": "sha512-UHNx/zKesgkZYQ12PiXtC0ZbIP0GVM3znNNBsxyBlZyqllwdpPeTrHFjjfkgdl/ybwUwAS2rdDTDkOH7GOJMWg=="
     },
     "espree": {
       "version": "3.5.4",

package.json

@@ -48,7 +48,7 @@
     "cross-env": "5.1.4",
     "css-loader": "0.28.11",
     "escape-html": "1.0.3",
-    "esm": "3.0.26",
+    "esm": "3.0.28",
     "events": "2.0.0",
     "express": "4.16.3",
     "fg-loadcss": "2.0.1",