Attach null stdio to pass nvm-windows check

https://github.com/coreybutler/nvm-windows/blob/6284f0ec44040764dc269144a3433664bf089646/src/nvm.go#L188
https://github.com/coreybutler/nvm-windows/blob/6284f0ec44040764dc269144a3433664bf089646/src/nvm.go#L73

In nvm-windows, if stdout isn't a character device, it shows an error dialog and waits for user input before terminating

Attach /dev/null to make sure that nvm-windows doesn't need intervention (https://nodejs.org/api/child_process.html#optionsstdio)

Author: timgblack

README.md

@@ -1,8 +1,8 @@
 <a name="check-node-version"></a>
 # check-node-version
 [![NPM version](http://img.shields.io/npm/v/check-node-version.svg?style=flat-square)](https://www.npmjs.org/package/check-node-version)
-[![AppVeyor build status](https://img.shields.io/appveyor/ci/parshap/check-node-version/master.svg?style=flat-square)](https://ci.appveyor.com/project/parshap/check-node-version/branch/master)
-[![Travis build status](http://img.shields.io/travis/parshap/check-node-version/master.svg?style=flat-square)](https://travis-ci.org/parshap/check-node-version)
+[![AppVeyor build status](https://img.shields.io/appveyor/ci/timgblack/check-node-version/be-a-terminal-for-nvm-windows.svg?style=flat-square)](https://ci.appveyor.com/project/timgblack/check-node-version/branch/be-a-terminal-for-nvm-windows)
+[![Travis build status](http://img.shields.io/travis/timgblack/check-node-version/be-a-terminal-for-nvm-windows.svg?style=flat-square)](https://travis-ci.org/timgblack/check-node-version)
 
 Check installed versions of `node`, `npm`, `npx`, `yarn`, and `pnpm`.
 

tools.js

@@ -42,7 +42,7 @@ function hasNvm() {
    // check for existance of nvm
    execSync(
      'nvm',
-     { stdio:[] } // don't care about output
+     { stdio: 'ignore' } // don't care about output
    );
   } catch (e) {
    // no nvm,