First draft of safe_input.py

-Adds safe input function, which accepts a prompt and returns the user input, returning None if an EOFError or KeyboardInterrupt exception is thrown
-Adds an if name == main block to test
First draft of trigrams.py

-Reads sherlock_small.txt into a list, splitting on spaces
-Iterates through list to create a dict of trigrams
-Does not parse strings yet
Adds random trigram selection and writes trigrams to new file
Corrects dict_set.py and removes DS_Store from repo

-Rewrites set section to create sets of numbers divisible by 2,3, and 4
-DS_Store should now be ignored globally