Adding support for Introductions

[martinheidegger]

Reviewing the response we got so far from NodeSchool Osaka we came to this possibly important way to improve workshoppers: When we have a NodeSchool there is need to explain what a workshopper is, how its used and . I think this process is something that people studying at home miss a little but also for the people in a school: Having it written out clearly might help a lot:

(first time of ever using any workshopper)

Congratulations! You have started a Workshopper for the first time!
Wait what? Workshopper? Yes! learnyounode is only one of many workshoppers.
They all work in the same way!
Probably you are wondering right now: "What does a workshopper do?". Let me explain:
Every workshopper will give you a list of challenges. You can select any challenge you like but if you
are new to the topic we recommend you to do them from top to bottom.
For every challenge you need to write a solution in code!
When you select a challenge it will show you want your code needs to do at the top and some hints that will surely help you to create a solution. (The hints are often really useful!)
Once you selected a challenge the workshopper will remember that challenge and with a subsequent call like learnyounode verify my_first_solution.js you can find out if your code passed that challenge.

That's all there is to it!
[Continue to learnyounode]

(then: first start of a workshopper like learnyounode)

Welcome to learnyounode!
The challenges in Learnyounode will teach you the basics of working with Node.js!
Node.js is a JavaScript execution system that allows you run JavaScript outside of a browser.
You can do a lot of programming outside of the browser! The challenges provided are all very basic but the concepts will help you a lot when you use node in future.
[Continue to the Challange selection]

I will try to work on a PR unless you have a problem with it.