reading data in from file.  changed computeScore to computeScoreTwo to take two arguments (users) to compute the score between them given a data set with multiple users.
fixed computeScoreTwo to return None instead of 0 when users have no shared preferences.
Create first unit tests and .gitignore

Create some unit tests for the EuclidianDistance algorithm.  Created a
.gitignore file in order to track the excludes with the project.
Put most of the __init__.py code under 'main' because the unit tests
didn't like it outside of 'main'.