Write a program that will tell you whether a year is a leap year.
A leap year is a year divisible by 4 unless it is also divisible by 100. If the year is divisible by 400, it is a leap year.
leap_year?(1840) # => true
leap_year?(1989) # => false
leap_year?(2000) # => true
leap_year?(2014) # => false
leap_year?(2016) # => true
Add another method to output a human readable string.
leap_year_sentence(1989) # => "The year 1989 is not a leap year."
leap_year_sentence(2000) # => "The year 2000 is a leap year."