refactor: add setup npm script

Author: sis0k0

CONTRIBUTING.md

@@ -42,17 +42,9 @@ Before you submit a Pull Request, consider the following guidelines.
 ```bash
     git clone [email protected]:NativeScript/nativescript-cli.git
 ```
-* Install the node dependencies.
+* Run the setup script. This will initialize the git submodule, install the node dependencies and build with grunt.
 ```bash
-    npm install --ignore-scripts
-```
-* Initialize the submodule.
-```bash
-    git submodule init
-```
-* Fetch data from the submodule.
-```bash
-    git submodule update
+    npm run setup
 ```
 * Make your changes in a new `git` branch. We use the <a href="http://nvie.com/posts/a-successful-git-branching-model/">Gitflow branching model</a> so you will have to branch from our master branch.
 ```bash

README.md

@@ -431,9 +431,7 @@ How to Build
 ```
 git clone https://github.com/NativeScript/nativescript-cli
 cd nativescript-cli
-git submodule update --init
-npm install --ignore-scripts
-./node_modules/.bin/grunt
+npm run setup
 ```
 
 To use the locally built CLI instead `tns` you can call `PATH_TO_CLI_FOLDER/bin/tns`. For example:

package.json

@@ -10,6 +10,7 @@
   },
   "main": "./lib/nativescript-cli-lib.js",
   "scripts": {
+    "setup": "git submodule update --init && npm i --ignore-scripts && ./node_modules/.bin/grunt",
     "test": "node test-scripts/istanbul.js",
     "postinstall": "node postinstall.js",
     "preuninstall": "node preuninstall.js",