Merge pull request #144 from sergi/greenkeeper-istanbul-0.3.22

Updated istanbul to version 0.3.22

Author: sergi

package.json

@@ -31,7 +31,7 @@
   "devDependencies": {
     "concat-stream": "1.5.0",
     "ftp-test-server": "0.0.2",
-    "istanbul": "0.3.21",
+    "istanbul": "0.3.22",
     "mocha": "1.21.4",
     "mocha-istanbul": "0.2.0",
     "rimraf": "2.2.8",