Bump shell-quote from 1.6.1 to 1.7.3

Bumps [shell-quote](https://github.com/substack/node-shell-quote) from 1.6.1 to 1.7.3.
- [Release notes](https://github.com/substack/node-shell-quote/releases)
- [Changelog](https://github.com/substack/node-shell-quote/blob/master/CHANGELOG.md)
- [Commits](https://github.com/substack/node-shell-quote/compare/1.6.1...1.7.3)

---
updated-dependencies:
- dependency-name: shell-quote
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

package.json

@@ -38,7 +38,7 @@
     "nyc": "^11.4.1",
     "opn-cli": "^3.1.0",
     "prettier": "^1.14.3",
-    "serve": "^10.1.2",
+    "serve": "^6.4.4",
     "tap-nyc": "^1.0.3",
     "tap-spec": "^4.1.1",
     "tape": "^4.8.0",