Minor changes to readme - installation instructions

Hi Dj,
I've just made some minor changes to the readme's installation instructions for a couple of points that are necessary but not mentioned. i.e. installation and configuration of the STProjectMaker package.
Feel free to merge this in or make your own changes of course.   ;-)

On a separate note myself and @saschakiefer are working on a similar concept expect using the Yeoman.io framework for scaffolding out apps.
https://github.com/saschakiefer/generator-openui5

Our openui5 generate does not include any sort of snippets functionality, but it does setup the boilerplate for a working app (plain app, fiori-style app, etc) - similar to what you're doing with templates. We haven't published the latest changes to npmjs yet but you can see them in the "develop" branch. Still all an ongoing labour of love of course...