Minor change in formatting of the "download opml" alert in edit profile view.
Change in formatting so that the "delete account" alert in edit profile view looks better for non-admin users.

It still doesn't look totally right, because there is a white space where the "invite a friend" alert should be. But it's only temporary while the beta lasts, so it's good enough.
Show an alert when an invitation email has been resent.
When first sending an invitation, persist the unencrypted invitation token in the "unencrypted_invitation_token" attribute of the invited User instance.

This is necessary to resend invitations without generating a new invitation token and invalidating the new one. This would be undesirable for us, because it would invalidate older invitations emails without it being obvious for the inviter.

Unfortunately devise_invitable has no native way to persist the unencrypted token in the db. Luckily it implements an instance method that can be used to retrieve the raw token just after sending the invitation, which we can use to roll out our own persistence logic.
Increment by 1 the inviter's invitation count when first sending an invitation to an email address.

I was trusting that devise_invitable already was doing this, but it isn't. It's probably because of the config in the initializer, but I'm not gonna mess with it because I intend to manage invitations limit a bit differently from what devise_invitable assumes by default. It's simple enough to do it in our customized FriendInvitationsController.
WIP: acceptance tests for send invitations feature.
WIP: Acceptance tests for send invitation feature.

Currently failing: user should be able to sign up normally instead of accepting an invitation. Currently if an invitation has been sent to a user's email, he must accept the invitation; he's unable to sign up normally, a "email has already been taken" error appears.