Adding missing functionality to README

https://github.com/AdvancedCustomFields/acf5-beta/issues/57 https://github.com/AdvancedCustomFields/acf5-beta/issues/54
Signed-off-by: Elliot Condon <e@elliotcondon.com>
Merge branch 'master' of https://github.com/AdvancedCustomFields/acf5-beta