Change source folder name to src/

I am a bit clueless on how to organize Python projects when it comes to src folder, module names and references.
Since I did not know how to reference the modules when importing each other and such, I simply called the source folder name `skald/`, full path being `skald/skald`. A bit on the heavy side, so instead opting to change it to `src/` or `src/skald/` - Tictail inspired. Should perhaps open a SO question as well!