Mailchimp update seems to be broken

[mwillmott]

There's a cronjob that runs (which has also been moved across to GAE on the server-refactor branch) which is meant to update our Mailchimp list. We only have one master list, the update should do the following:

• Every time someone registers for a ride, add their email to the list
• Every time someone pays for a ride (so is fully registered), add them to the ride group on that list (the group id is added to the ride model)
• Update the mailchimp profile with the amount raised on their latest fundraiser (if they have one)

This cronjob is meant to keep the list in sync. This enables us to send emails to people who are doing (or have done) specific rides. We can also send emails to people who are below a fundraising threshold to encourage them to raise more (for example).

This update process appears to be broken. I haven't done any work to look at why so it might be a very easy fix.