Support smaller EC2 instance type

[Sjors]

Currently the minimum supported instance type is t2.small which costs about $20 per month, plus $2 for storage and a little bit for upload bandwidth to maintain blockchain karma.

I ran into out of memory crashes with the t2.micro, but a careful devops guru might be able to make things work on 1 GB RAM. That would cut costs in half.

Similarly storage requirements can probably be reduced from 20 GB to something closer to the 8 GB minimum, which could shave another dollar of the monthly bills.