Ensure specific 6to5 and 6to5-runtime version (temporary fix)

There's a bug with more recent versions, see #368.

Author: valeriangalliat

package.json

@@ -78,7 +78,7 @@
     "README.md"
   ],
   "dependencies": {
-    "6to5-runtime": "^3.3.3",
+    "6to5-runtime": "3.6.2",
     "chalk": "^0.5.0",
     "concat-stream": "^1.4.7",
     "docopt": "^0.4.1",
@@ -101,7 +101,7 @@
     "vinyl-source-stream": "^1.0.0"
   },
   "devDependencies": {
-    "6to5": "^3.3.4",
+    "6to5": "3.6.2",
     "coveralls": "^2.11.2",
     "dateformat": "^1.0.11",
     "istanbul": "^0.3.5",