update sha.js to 2.3.4 - performance improvements for sha1

Author: dominictarr

package.json

@@ -23,7 +23,7 @@
     "pbkdf2-compat": "2.0.1",
     "public-encrypt": "1.1.2",
     "ripemd160": "0.2.0",
-    "sha.js": "2.3.2"
+    "sha.js": "2.3.4"
   },
   "devDependencies": {
     "tape": "~2.3.2",