feat: enable different conf for each type

Thanks to that little change writing configuration like this will work:

```coffeescript
bump:
  options:
    commitMessage: 'v%VERSION%'
    push: false

  minor:
    options:
      push: true
      pushTo: 'canary'

  major:
    options:
      push: true
      pushTo: 'origin'
```

Closes #84