Rename babel's es6.parameters.rest option to es6.parameters

The old name was deprecated and spits out a bunch of annoying log
messages now.

See https://github.com/babel/babel/commit/c0fd4c1f9e0b18231f585c4fa793e4cb0e01aed1

packager/react-packager/.babelrc

@@ -10,7 +10,7 @@
     "es6.constants",
     "es6.classes",
     "es6.destructuring",
-    "es6.parameters.rest",
+    "es6.parameters",
     "es6.properties.computed",
     "es6.properties.shorthand",
     "es6.spread",

packager/transformer.js

@@ -23,7 +23,7 @@ function transform(srcTxt, filename, options) {
       'es6.blockScoping',
       'es6.classes',
       'es6.destructuring',
-      'es6.parameters.rest',
+      'es6.parameters',
       'es6.properties.computed',
       'es6.properties.shorthand',
       'es6.spread',