Update publish script and lerna version

lerna.json

@@ -1,5 +1,5 @@
 {
-  "lerna": "2.0.0-beta.38",
+  "lerna": "2.4.0",
   "packages": [
     "jupyterlab",
     "jupyterlab/tests/mock-mimeextension",

package.json

@@ -18,7 +18,7 @@
     "docs": "lerna run docs",
     "get:dependency": "node scripts/get-dependency.js",
     "integrity": "node scripts/package-integrity.js",
-    "publish": "npm update && npm install && npm run clean && npm run build:packages && lerna publish -m \"Publish\"",
+    "publish": "npm update && npm install && npm run clean && npm run build:packages && lerna publish --force-publish=* -m \"Publish\"",
     "test": "cd test && npm test",
     "test:services": "cd packages/services && npm test && npm run test:integration && cd examples/node && python main.py",
     "test:chrome": "lerna run test:chrome --stream",
@@ -34,6 +34,6 @@
   },
   "dependencies": {},
   "devDependencies": {
-    "lerna": "2.0.0-beta.38"
+    "lerna": "^2.4.0"
   }
-}
+}