Hi,

I have removed a sentence where there was an explanation about the `required=true` statement in the @RequestMapping explanation section, since it's not there in this tutorial.

I guess it's a copy/pasta mistake since this parameter is indeed present in the Spring MVC Web tutorial :+1:

At the bottom of the document (above the footer), I added links to other guides that readers may find to be useful.

It's nice to see all the steps that we have to do, but it requires for example
- JDK 1.8 or later
- Gradle 2.3+ or Maven 3.0+
- git to clone the project or download and extract a zip file

whereas here, by using the following button, we only have to click on it ("Workspace Developer" button)
then we can try and develop spring rest service from the web browser.

Link was broken due to missing 's' i.e. **http://docs.spring.io/spring/doc** v **docs**

Resolves #32