Calculate a proficiency score based on exponential moving average
Proficiency score uses exponential moving average weighted with question difficulty
Mark assignment complete if proficiency > 1
Mark assignment as complete if proficiency > 1 and completed at least one level 3 question. 1 very long line of code in answer question use case
Fix obsolete tests
Merge pull request #36 from bmprovost/proficiency-algorithm

Proficiency algorithm