Greeting Builder

Build a small greeting helper. The main function, `createGreeting`, should take a person's first name, last name, and time of day, then return one greeting string.

1. `formatName(firstName, lastName)` should return the first and last name as one string.
2. `getGreeting(timeOfDay)` should return `"Good morning"`, `"Good afternoon"`, or `"Good evening"`.
3. `createGreeting(firstName, lastName, timeOfDay)` should use the other two functions and return the final greeting.