renamed width/height attribute
added accessor for stepTime
New build scheme

We now use the release script provided by MisterDA (see love-release.sh).
The build and run is done by:
* moving resources (./res directory) to ./gen_love
* compiling .moon files into ./gen_love
* launching the release script on ./gen_love, thus creating a .love file in ./gen_love/build
* launching the created .love file

+ We added a cc-licensed song which will be used later