a new instance of orange tree should have an age of 0
a new instance of orange tree should have a height of 0
refactor initialize specs, and tree should age after time passes
tree should grow in height as tree ages, but it should stop growing after 31 years
a new instance of an orange tree should have 0 oranges (or orange_count = 0)
every year, the orange tree should lose all its oranges, and then grow between 17 and 50 oranges
tree should die after 31 years
the user should receive an error if they try to pick oranges from a tree without any