Invitation screen should indicate that a user has already been invited to a ride

[bakermo]

When inviting friends to a ride, the UI presented should indicate if certain users on my friends list have been invited (by anyone).

1. The checkbox should be removed and the already invited user should not be selectable
2. Invited users should be sorted to the bottom of the list
3. Invited users should have a tag and icon on their list item to indicate that they have already been invited

This is what the UI looks like today. It does not indicate the user has already been invited, it allows me to invite again. There is no harm from a data standpoint; this operation is idempotent, i.e. my friend will only ever be invited once, but I have no indicator that I have already invited them.