#86: add BestTime and Distance models
#86: add BestTime and Distance to django admin
#86: add fixtures for distances
#86: add test for distances.distance_km property
#86: add creating / updating BestTime objects on Workout save
#86: add test for auto creating BestTime objects
#86: add test for auto updating BestTime objects
add tests for management command set_password
 #84: add one more case for routes tests
#86: add unique together constraint in Distance model