Added sync job for withings

This is the job class that will get scale data from withings
This spec and the one previously has the same description of `validates user`.

A better way to write this would be:

```ruby
context 'validates user' do
  context 'when valid user' do
  end

  context 'when user is nil' do
  end

  context 'when non user type' do
  end
end
```