Wk3 hwk & Wk2 hwk updates

Only the files in the folders are updated. Key updates:
- Final Project / Proposal
- Week 3 / API GOV P2V2 (minor updates to clean up the detail message)
- Week 3 / Apt_Main 
- Week 3 / lib (classes for Apt_Main)
- Week 3 / SecretNumber
- Week 3 / lib_sn (classses for SecretNumber)
Because `unit.occupied?` already returns a boolean, you don't need to make a comparison to `false`. What does this line reduce to then?