Teenager
Write a function called isTeenager that takes in a number argument called age and returns true or false if this person is a teenager
To run the specs follow these commands:
# first install the new gem to run the tests
gem sources -a http://flatiron:33west26@gems.flatironschool.com
gem install learn-co
# to run in the command line run
learn
#to run in the browser
learn -b