fix(package): fix regeneratorRuntime error

Properly polyfill async functions for use in es5 env
Add `babel-plugin-transform-runtime` devDependency

fixes #51 `ERROR build:compile ReferenceError: regeneratorRuntime is not defined`

Author: medfreeman

Diff for: package.json

@@ -35,6 +35,7 @@
     "babel-eslint": "^8.0.0",
     "babel-plugin-transform-decorators-legacy": "^1.3.4",
     "babel-plugin-transform-object-rest-spread": "^6.26.0",
+    "babel-plugin-transform-runtime": "^6.23.0",
     "babel-preset-env": "^1.6.0",
     "codecov": "^3.0.0",
     "cross-env": "^5.0.5",
@@ -64,6 +65,7 @@
   "babel": {
     "presets": "babel-preset-env",
     "plugins": [
+      "transform-runtime",
       [
         "transform-object-rest-spread",
         {

Diff for: yarn.lock

@@ -934,7 +934,7 @@ babel-plugin-transform-regenerator@^6.22.0:
   dependencies:
     regenerator-transform "^0.10.0"
 
-babel-plugin-transform-runtime@^6.15.0:
+babel-plugin-transform-runtime@^6.15.0, babel-plugin-transform-runtime@^6.23.0:
   version "6.23.0"
   resolved "https://registry.yarnpkg.com/babel-plugin-transform-runtime/-/babel-plugin-transform-runtime-6.23.0.tgz#88490d446502ea9b8e7efb0fe09ec4d99479b1ee"
   dependencies: