Setup example mocha test
Implement numeric cases
Fix README for Relationship Directions problem
Complete implementation of relation directions problem
Revise implementation to pass tests from Udacity

The instructions seem to differ significantly from the automated tests
written here:
https://www.udacity.com/course/viewer#!/c-ud804/l-3077038869/e-3316998582/m-3318328556

:(
Implement alphabetizer
Record problem 3: PSI