Updated package.json

Bumped version for laravel-elixir to 6.0.0-14 in which various npm errors and warnings have been fixed (laravel/elixir#679).

package.json

@@ -8,7 +8,7 @@
     "bootstrap-sass": "^3.3.7",
     "gulp": "^3.9.1",
     "jquery": "^3.1.0",
-    "laravel-elixir": "^6.0.0-11",
+    "laravel-elixir": "^6.0.0-14",
     "laravel-elixir-vue-2": "^0.2.0",
     "laravel-elixir-webpack-official": "^1.0.2",
     "lodash": "^4.16.2",