Bump bunyan version to 1.7.1

Unfortunately, the old version of bunyan we were depending on has a
compilation failure during npm install, so we need to upgrade it in
order to get more builds.

Fixes #6487

package.json

@@ -84,7 +84,7 @@
     "boom": "2.8.0",
     "bootstrap": "3.3.5",
     "brace": "0.5.1",
-    "bunyan": "1.4.0",
+    "bunyan": "1.7.1",
     "clipboard": "1.5.5",
     "commander": "2.8.1",
     "css-loader": "0.17.0",