Remove babel-runtime and replace babel Symbol

.babelrc

@@ -6,7 +6,6 @@
     "/node_modules/"
   ],
   "plugins": [
-    "transform-runtime",
     "transform-react-constant-elements",
     "transform-react-inline-elements",
     "closure-elimination"

package.json

@@ -50,7 +50,7 @@
     "immutable"
   ],
   "dependencies": {
-    "babel-runtime": "^6.11.6",
+    "es6-symbol": "^3.1.0",
     "rxjs": "^5.0.0-beta.10"
   },
   "devDependencies": {

src/util/isIterator.js

@@ -1,4 +1,6 @@
+import _Symbol from 'es6-symbol'
+
 export default function isIterator(arg) {
-  return typeof arg[Symbol.iterator] === 'function'
+  return arg && typeof arg[_Symbol.iterator] === 'function'
 }
 

src/util/isObservable.js

@@ -1,8 +1,9 @@
+import _Symbol from 'es6-symbol'
 import { Observable } from 'rxjs'
 
 export default function isObservable(obj) {
-  return typeof obj === 'object' && (
-    typeof obj[Symbol.observable] === 'function' ||
+  return obj && (
+    typeof obj[_Symbol.observable] === 'function' ||
     obj instanceof Observable
   )
 }