Add some development dependencies

This is just so I can get the thing running on my machine.
Create a class for toughness measurements
Create a new table for toughness measurements

It looks like when the schema was previously put together it had some extra
bits about plpgsql and btree, not sure what this is, should ask Jo.

    # These are extensions that must be enabled in order to support this database
    enable_extension "plpgsql"
Install rspec
Define some basic tests for the toughness measurement

I know that the measurement won't be valid with so little information,
I just want to have this set up in a testing framework from the start.
Create a TODO list