feat(plugins): run verifications in series

With this new feature you can pass an array of plugin locations/names to
both "verifyConditions" and "verifyRelease" in your `package.json`'s "release"
field. This will run multiple verification plugins in series.

package.json

@@ -36,6 +36,7 @@
     "parse-github-repo-url": "^1.0.0",
     "require-relative": "^0.8.7",
     "run-auto": "^1.1.2",
+    "run-series": "^1.1.2",
     "semver": "^5.0.1"
   },
   "devDependencies": {