Issue title: Automate release process
 Issue body: We should have an `npm` script (e.g.: `release`) that will:

- [ ] Update the `CHANGELOG.md` (see: #345)
- [ ] Tags a new version and updates the [release](https://github.com/sonarwhal/sonar/releases).
- [ ] Publishes a new version on `npm`.
- [ ] Other ?
 Comments: 
 Comment 0: - [ ] Triggers a site update.
 Comment 1: * [] publishes a tweet with a link to the changelog?
 Comment 2: > publishes a tweet with a link to the changelog?

The whole point of having the release process more automated is to release often, so I haven't implement that as I don't think it's a good idea to tweet about every single version. 

We could have an option to only tweet about major versions, but yet again, my opinion is that in general we should tweet also about versions that include important changes (e.g.: a new connector was added), plus, tweets should include something unique about the release they are talking about.


 Comment 3: OK, there's always time to add it later.
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