Create .babelrc (#2466)

When I was going through the documentation about creating custom builds
I ran into the error outlined at the below link. Applying the suggested
fix solved it so I'm submitting same here.

http://stackoverflow.com/questions/30386317/babelify-throws-parseerror-o
n-import-a-module-from-node-modules

See https://github.com/almende/vis/pull/2460

.babelrc

@@ -0,0 +1,3 @@
+{
+  "presets": ["es2015"]
+}