set up building class

* add address attribute as accessor to be entered upon creating the object and also easily manipulated in the future.
add apts attribute

* creates the instance var apts as an empty array to accept "many apts"

* is NOT set to accessor so it can not be set via methods.
oops- my class set up was all messed up- i made corrections to fix this
set up basic structure for tentant class
set basic structure for tenant class

* set name, age and credit as accessor attributes

* set credit rating method as a case
make changes to credit rating def

* reversed order of ratings to get correct response
set up apartment class
create add-tenant and remove_tenant methods

- still need testing
make adjustment to add_tenant and remove_tenant: they work!
all methods are working nicely
add methods total sqaure feet and monthly revenue

- using map to search the apts array and create a new array, then reduce and add together the items in the array.
make adjustment on remove_apt
create tenant list method

- by selecting from the tenants array and making a new array with tenant names
test building class for initializer- check

test add apt - check

test remove apt - error

test total sqaure feet - check

test monthly revenue - check