upgrade acorn

lib/6to5/util.js

@@ -221,14 +221,15 @@ exports.parse = function (opts, code, callback) {
     var tokens   = [];
 
     var ast = acorn.parse(code, {
-      allowReturnOutsideFunction: true,
-      ecmaVersion:                opts.experimental ? 7 : 6,
-      playground:                 opts.playground,
-      strictMode:                 true,
-      onComment:                  comments,
-      locations:                  true,
-      onToken:                    tokens,
-      ranges:                     true
+      allowImportExportEverywhere: true,
+      allowReturnOutsideFunction:  true,
+      ecmaVersion:                 opts.experimental ? 7 : 6,
+      playground:                  opts.playground,
+      strictMode:                  true,
+      onComment:                   comments,
+      locations:                   true,
+      onToken:                     tokens,
+      ranges:                      true
     });
 
     estraverse.attachComments(ast, comments, tokens);

package.json

@@ -35,7 +35,7 @@
     "test": "make test"
   },
   "dependencies": {
-    "acorn-6to5": "0.9.1-14",
+    "acorn-6to5": "0.9.1-16",
     "ast-types": "~0.6.1",
     "chokidar": "0.11.1",
     "commander": "2.5.0",