Support for seach and thumbnails

I needed to extend the client to support search and thumbnails. As I was using the client for the first time I also discovered some inconsistencies in the returned values. Sometimes it was the response object, sometimes the json object. It lead me down a bit of a rabbithole and I ended up moving quite a few things around (and more than once). I am personally fairly happy with the current state of it, but it is probably a bit opinionated. 

I should really have made more separate pull requests, but since I was in a hurry to get the changes done for Podio, I wasn't very organized in my changes. 

So take it, parts of it, or reject it, it's all up to you :)