New GitHub organization and ongoing support

[charlie-foxtrot]

@gabeschine has graciously offered to help support rtl_airband in the near term.

I have converted the repo from "personal" to "organization" so he has the ability to merge PRs. As a result the URL has changed to https://github.com/rtl-airband/RTLSDR-Airband

There may be a few bumps as the automation moves over, but he has been able to merge his first PR #499

I do plan to resume working on rtl_airband, but in the meantime the repo is in good hands.

Thanks again @gabeschine!