Some condensation

- Condensed a little bit more the text and snippets 
    - Only to illustrate how the path changes
    - Removed `sass()` and watcher function, only `src` and `dest`
- Removed the first snipped since the first one suffices to explain what happens with the base and relative path.
- Removed the mention to the `callback` 
- Split the code snippets for two cases: 
   - Be explicit about the base 
   - Don't change the base but write a different destination folder