doc: use `Node.js` in synopsis document

Change an instance of `Node` in the synopsis document to `Node.js.`

PR-URL: https://github.com/nodejs/node/pull/6476
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>

doc/api/synopsis.md

@@ -5,7 +5,7 @@
 `node [options] [v8 options] [script.js | -e "script"] [arguments]`
 
 Please see the [Command Line Options][] document for information about
-different options and ways to run scripts with Node.
+different options and ways to run scripts with Node.js.
 
 ## Example