"30-second intro to OOP" needs a new home

[brian-rose]

As discussed in #38, the section in the datetime notebook "30-second intro to Object Oriented Programming" belongs somewhere else earlier in the Foundations sequence.

To be dealt with later...

[dcamron]

If you want to leave this open even after #81 as a reminder to have this material pop up elsewhere, we can.

[brian-rose]

Yes, I would leave this open as a reminder to find a new home for the material (and also where to find it in the old commits).

[brian-rose]

We need to find a home for this. Perhaps it will fit with "How to build a python package" material.