Add a not about test setup
Add a not about test setup

Add an example of database cleaning strategy for test environment and
add a note about setting a different namespace in test init. The latter
is important to prevent development data deletion when `RAILS_ENV` is
not set to 'test' for any reason.

cavi21/Dynamoid,Dynamoid/Dynamoid,Dynamoid/Dynamoid,cavi21/Dynamoid