fix&feat: fix subscribe plan's subdomain & add hourly forecast method

[timsu27]

1. fix subscription plant's from 'api' to 'pro' according to document, reference: https://openweathermap.org/api
2. add support of interval 'hourly' for hourly forecast, which applies to all weather_manager's forecast methods.

[csparpa]

@timsu27 thanks for this. Could you please apply the same Pull Request to the develop branch instead ? No PRs allowed on the master branch during development thanks

[csparpa]

@timsu27 And don't forget to add yourself to the CONTRIBUTORS.md file also