a few changes to make for valid test functionality

Hey Ken! 

This is awesome. Thanks, man.

There's only a few changes to make here. I think when I copied and pasted a few spacing differences came up. The main changes are:

Lines 62-64: The method should be #map, not #map_by. With that fix, however, 5 players were found in the database from previous tests (LeBron and Kyrie Irving). So, I reworded the test to reflect that. I imagine you could change it to say "Two players are already in the database, add these three..." etc..

Lines 139-140: Same as above...you had already created the Celtics to the database.

Again, thanks a lot for this...was was really good practice!