This also includes documentation to state which methods actually support media download, and how to achieve that. Added TODO to not forget we should tell the user how to achieve these kinds of things. Fixes #21
Instead of depending on the google go client API repository, I now use the original data source, namely the discovery API. fixes #5
It's about time we finish up this part, to make it even easier to test against more APIs, and keep them up-to-date