This is cool, but why do I have to enter a source in the sync options? At least there should be a default.
The content type of the source edit field should probably be url, so you get the / etc. And the username field should not capitalize the first letter.
I'm also getting a bug in that the settings page doesn't scroll all the way down, so the save button cannot be activated.
Also I'm wondering, why don't you use theme.inverted for the dark theme?