Fix exceptions

Currently babel-runtime versions newer than 6.5.0 swallows
exceptions and causes async-retry blocks to return 'undefined' as
a return value.

package.json

@@ -55,7 +55,7 @@
     "arr-flatten": "1.0.1",
     "array-unique": "0.3.2",
     "async-retry": "0.2.1",
-    "babel-runtime": "6.11.6",
+    "babel-runtime": "6.5.0",
     "bytes": "2.4.0",
     "chalk": "1.1.3",
     "copy-paste": "1.3.0",