#1212 Move to use `fetch` instead of `xhr`

Originally at 2015-12-09T22:09:33Z by Herbert Vojčík With `amber-compat-fetch` to add the polyfill. <bountysource-plugin> --- Want to back this issue? **[Post a bounty on it!](https://www.bountysource.com/issues/28996362-move-to-use-fetch-instead-of-xhr?utm_campaign=plugin&utm_content=tracker%2F79201&utm_medium=issues&utm_source=github)** We accept bounties via [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F79201&utm_medium=issues&utm_source=github). </bountysource-plugin>