Add the missing reblog info fields to Post

[KevinTCoughlin]

Overview

This adds the missing reblog_* fields to Post.java brought up in #76.

Concerns

• I'm unsure about the JavaDoc accuracy for the new Getters. Also this documentation seems to be missing on https://www.tumblr.com/docs/en/api/v2 cc: @ceyko
• Add tests? Our testing solution is lacking. I can follow the style that exists in TextPost for example, but I'd like to just inflate a flat JSON file down the road or something.

Example existing test:

        Map<String, Object> flat = new HashMap<String, Object>();
        flat.put("type", "text");
        flat.put("title", title);
        flat.put("body", body);
        flat.put("note_count", noteCount);
        flat.put("reblogged_from_id", rebloggedFromId);
        flat.put("reblogged_from_name", rebloggedFromName);
        Gson gson = new GsonBuilder().registerTypeAdapter(Post.class, new PostDeserializer()).create();
        post = (TextPost) gson.fromJson(flatSerialize(flat), Post.class);

[ceyko]

Maybe just update the doc for the root varieties to say that they're the data for the root post / root post's blog.

Agree, tests are a bit weak. I'm good either way - adding them or not.

Will update the api docs to reflect these fields.