Ignore it.

Cloudflare themselves have stated that these are fake - see https://blog.cloudflare.com/empty-ddos-threats-meet-the-armada-collective/ I highly recommend that you read this article, as it is a very clear explanation from the front line. 
The armada collective is a real DDOS group, but some con artists are just using their name to try to scare people. The Bitcoin address is apparently the same on all their emails, which means that they will never know who has paid them.  
It is possible to track the amounts paid to a Bitcoin address and it seems they have made over $100K from this scam!  

Bottom line, DDOS threats should be backed up by proof (perhaps a DDOS of 15 mins) before you pay up.

EDIT: Just to clarify, I don't mean to give an opinion whether payment should be made or not. As wildcard says, always have good security, and if you decide to pay, check that the threat is legitimate first.