CloudFlareError
CompareAndSet()

To soon replace compareAndUpdate()
rename differenceExpected/differenceActual
Split Compare() and Update()
Move cf.Compare() to CompareConfigItems()
Alphabetise config_items
s/CloudFlareConfigItem/CloudFlareSetting/
CloudFlareSettings.ConfigItems()
convertToConfig() -> settings.ConfigItems()
ConfigItemsForUpdate to store current/expected

So that we can log what value a key is changing from/to.
Logging in Update()

Occurs before each call to Set() so that we can see progress.