Update it-IT translation

- Aligned the translation to all the recent changes.
- Fixed some typos.
- Refactored some sentences for a better understandable meaning..
Add my reference links
Merge branch 'update-contributors' of https://github.com/Ragnarokkr/idiomatic.js

* 'update-contributors' of https://github.com/Ragnarokkr/idiomatic.js:
  Add my reference links