vue*: update outdated pages to latest Vue.js version.

Update the examples of the following pages to the latest Vue.js version:

 - vue.md
 - vue-init.md
 - vue-build.md
 - vue-serve.md

pages/common/vue-init.md

@@ -0,0 +1,16 @@
+# vue init
+
+> Legacy project initialization subcommand of the Vue.js framework.
+> More information: <https://cli.vuejs.org/guide/creating-a-project.html#pulling-2-x-templates-legacy>.
+
+- Create a new project using one of the default templates:
+
+`vue init {{webpack|webpack-simple|browserify|browserify-simple|simple}} {{project_name}}`
+
+- Create a new project using a local template:
+
+`vue init {{path/to/template_directory}} {{project_name}}`
+
+- Create a new project using a template from GitHub:
+
+`vue init {{username}}/{{repo}} {{project_name}}`