Add files 'sherlock.txt' and 'trigrams.py'

Add story 'sherlock.txt' and first draft of 'trigrams.py' to repo.
Modify 'trigrams.py'

Condense code and improve efficiency of for loop in 'trigrams.py'
Add 4-gram changes to 'trigrams.py'

Add new code for 4-gram output in 'trigrams.py'.
Combine unnecessary lines of code in 'trigrams.py'

Combine for loops and delete unnecessary code in 'trigrams.py'
Add 3 characters key in 'trigrams.py'

Add more code for 3 characters key input in 'trigrams.py'
Add final version of 'trigrams.py'

Add final version of 'trigrams.py' homework with comments.
Also, add 'sherlock.txt', which is to be used with 'trigrams.py'.