Added logic to use the plural or singular form of the time (eg. day(s) o...

Added logic to use the plural or singular form of the time (eg. day(s) or year(s)

Created a isPlural function that takes in the number and the string you
want it to output. It returns the string, either with or without an "s".

Now, if there is 1 day in the timer, it will say 1 day instead of 1
days. Same for years, hours, and minutes.