remove uri check which breaks non-http uris

The SOUP_URI_VALID_FOR_HTTP check invalidated any non http/https URIs.
This affected the proxy function so that socks proxy would not work. It
would also cause luakit to fail to start if an invalid uri was marked as
the active proxy in the proxymenu file.
Merge pull request #3 from glindste/fix_socks_proxy

remove uri check which breaks non-http uris