Implement Tumblr service

[Warrows]

I'm using the rss feed. But a service fetching specifics tumblr blog posts and displaying them given their type (images, videos, links, text...) would be great.

[haschek]

Please provide links to API docs if you request a new service class.

[fernand0]

The api is here: https://www.tumblr.com/docs/en/api/v2