Your original hello world + one test, a .gitignore skeleton and requirements downloadable with pip

Hi Mattia.
I took your Hello World app and refined it just a bit.
The web-app itself is the one you wrote (I cherry-picked it).

In this PL you will find these enhancements:

* `.gitignore` just ignores python compiled `.pyc` files and OS X's `DS_Store` files. `.pyc` files themselves has been purged from the repository

* the binary requirements (flask, python and so on) have been wiped out. They can be installed with the (dead stupid) build script `build.sh`: this just run `pip install` reading the list of requirements stored in `requirements.txt`. Caution: use it after having activated the virtualenv with

```
source bin/activate
```

* I managed to create a simple end-2-end test: it just assert that the home page returns 200 and contains the world Hello.



This PL also contains the first specification blueprint.