add another foaf to demonstrate failures

in trying to build a failing test for #104, i added another foaf so that the foaf queries in the tests would match 2 friends rather than just one.  in adding this extra triple, i think i've uncovered a number of other issues.  i've opened this PR as a way to have a discussion around whether or not my expectations are correct.  i'll make more specific notes on the commit to help give context for the discussion.
You are definitely right about the _bug_, but you are wrong about eh query planner.

Each step is running _in parallel_ if it is sort-joinable (with solutions that flows in a pipeline), and _in series_ if it is a basic join (with solutions that flows in a pipeline). The model is definitely _complex_ but fast. The difference between the two is that the first only activate a single ReadStream from LevelUp, while the second creates a ReadStream for each partial solution. As you can imagine, the first is way faster. However, the first cannot be applied to all cases, and the query planner job is to check which type of join to use. The ordering based on size is _non relevant_, as all steps **should be created to run in whatever order** because a Graph pattern is declarative.

Can you please verify that passing `{ joinAlgorithm: 'basic' }` to force the basic join, so we can check if it's the query planner or worse.