create 2 methods for string manipulation

* create method splits() to produce an array from normalized text

* create method unique() to produce an array of unique words (no repeats) from normalized text
create method to count the number of words in a string

* split string into an array and count the number of indexes in the array
create a parameter for method counts that gives an option to count unique words in a string

* I tried to use keyword argumentd originally, but I couldn't get it to work.
w
create a method that takes a string and counts the number of duplicate words and returns a hash with the word and count.

* first, create an array from the string

* then, group by word and separate into new arrays with their count with .map

* last step flatten array and transform to hash.
create method to find most common word in string

* make a hash using word_hash_count

* select items in that hash with words greater than length 3

* find the word with the highest count