Update Node.js version in Readme (#1617)

Please do not merge manually, we are trying out the auto-merge bot. 

@sofisl would the bot respect the `do-not-merge` label?

Author: fhinkel

README.md

@@ -17,7 +17,7 @@ on Google Cloud Platform.
 
 ### Prerequisites
 
-1. Install [Node.js version 8 or greater][node]
+1. Install [Node.js version 10 or greater][node]
 1. Clone this repository:
 
         git clone https://github.com/GoogleCloudPlatform/nodejs-docs-samples.git