chore(package): update shower-core to version 2.0.7

https://greenkeeper.io/

package.json

@@ -27,7 +27,7 @@
     "README.md"
   ],
   "dependencies": {
-    "shower-core": "^2.0.6",
+    "shower-core": "^2.0.7",
     "shower-material": "^1.0.5",
     "shower-ribbon": "^2.0.6"
   },