MTA and Rental Labs

# MTA Lab
Could be improve quite a bit. On my TODO list:
1. put separate arrays in a hash so that future lines can be added
2. use ABS function instead of conditional logic to prevent negative values
3. add user validation
4. traverse arrays to display station options to user

# Rental Lab
Unfinished. Functionality implemented:
* List Tenants
* Create Tenants

Further work required to implement some of the other menu options.