Add hint on even/odd operator, moved exersise down one paragraph (thw-python)

This PR 

* provides a hint and example usage for the modular division operator, which is not especially familiar to our audiences
*  moves the "create three variables with the following types" exercise to follow the paragraph on type coercion on which it depends.

These respond to unfamiliar-with-% operator and you-didn't-tell-us-how-to-do-that-yet student hangups.