Adding a note about restrictions on subnets that apply to ELB and RDS, slightly more nuanced than "just check all the boxes". See http://discourse.metabase.com/t/cannot-setup-on-aws-in-vpc/2166 for more detail.

Fixing step3 to point to the correct URL which is:
https://github.com/metabase/metabase-buildpack

Change the recovery instructions to match the new path used in docker
containers.
Include a new section on finding a stopped metabase container.
Make the instructions on using shared/host volumes safe.