updated jwcrypto to use optimized libraries

package.json

@@ -25,7 +25,7 @@
     , "colors" : "0.5.0"
     , "sax" : "0.2.3"
     , "mimelib-noiconv" : "0.1.3"
-    , "jwcrypto": "https://github.com/mozilla/jwcrypto/tarball/7504350"
+    , "jwcrypto": "https://github.com/mozilla/jwcrypto/tarball/83aa543"
   }
   , "scripts": {
     "postinstall": "./scripts/generate_ephemeral_keys.sh",