fix: reactjs demo during yarn install, fixes #145

simply remove unused dependencies fixes this issue, but I removed
all package-lock.json / yarn.lock since the demo should always be
in sync with the codebase

demo/express/package.json

@@ -10,6 +10,7 @@
   "author": "harttle",
   "license": "MIT",
   "dependencies": {
-    "express": "^4.14.0"
+    "express": "^4.14.0",
+    "liquidjs": "*"
   }
 }