Makefile: loaddata suggestion for default command

[niceguydave]

Summary

When running the default command in the Makefile, (I simply ran make) there is is currently an error when trying to load the special_squares fixture.

Proposed fix

• Adding the correct name of the fixture to python manage.py loaddata... should help fix this (special-squares).
• I also imagine that we would want to include the special-square-types fixture, given that it exists as another file in the fixtures directory.

Impact

• This change allows the make command to run e.g. for anyone setting up the project for the first time.

Testing

• All existing tests pass.