added setup script in package.json, required to get eslint to work with arc

Reviewers: arik

Reviewed By: arik

Subscribers: ben

Differential Revision: https://phabricator.bitgo.com/D6108

Author: Zac Leids

package.json

@@ -62,6 +62,7 @@
     "express": "node bin/bitgo-express -b 0.0.0.0",
     "test-node": "./node_modules/.bin/istanbul test ./node_modules/.bin/_mocha -- --timeout 20000 --reporter list --recursive test/",
     "test-browser": "npm run compile-test && ./node_modules/karma/bin/karma start .karma.conf.js --log-level debug --single-run",
+    "setup": "git submodule add https://github.com/tagview/arcanist-extensions.git .arcanist-extensions; npm install -g eslint; git submodule update --init",
     "lint": "./node_modules/.bin/eslint --ext .js ."
   },
   "dependencies": {