Add main() function

Parses command line arguments, Accept rack of letters.

Signed-off-by: Prashant Malani <p.malani@gmail.com>
Add valid_words function

Add a helper function which takes a rack in
string form, and returns the list of valid words.

Also add a sample txt file to test out the function.

Signed-off-by: Prashant Malani <p.malani@gmail.com>
add score_word function

Add a function to return the score of a provided
word.

Signed-off-by: Prashant Malani <p.malani@gmail.com>