support babel-core@7 (#403)

Author: hzoo

package.json

@@ -13,7 +13,7 @@
     "object-assign": "^4.0.1"
   },
   "peerDependencies": {
-    "babel-core": "^6.0.0",
+    "babel-core": "6 || 7 || ^7.0.0-alpha || ^7.0.0-beta || ^7.0.0-rc",
     "webpack": "1 || 2 || ^2.1.0-beta || ^2.2.0-rc"
   },
   "devDependencies": {