GitHub plugin falsely detected as wordpress.org plugin

[Zodiac1978]

This plugin from the German community is wrongly reported as from wordpress.org (should be GitHub):
https://github.com/deworg/dewp-planet-feed

Additionally the "Tested up to" info is missing (maybe because it is looking on wordpress.org for this info).

[roytanck]

Off the top of my head: If no Update URI is specified in the plugin's header, wordpress.org is used as a default value. This is because WP itself handles it that way, and will attempt to get updates from there.

The tested up to value is usually specified in the readme.txt, which this plugin does not have. We could probably handle this better.