Separate out feed fetching functionality so that it can be re-used.
Integrate the Transport "mode" into the Transport "type" dropdown. It's unlikely that you'd have a client that's both push and pull and other.
XML Client: implement test_connection method, see #15
Move inline CSS into separate file.
Use checked() helper function, see #17
Remove unnecessary serialize call; add_post_meta will take care of that.
Another unnecessary serialize call before add_post_meta
XML Client: Clean up some up the styling on the Edit Site page, see #22