splango: added Variant in .models import sentence
splango: removed unused imports
example.myapp.tests: added models factory for Experiment, Subject and Variant
example.myapp.fixtures: added users fixture
example.myapp.tests: added test_declare_and_enroll() in InitTest class
example.myapp.tests: added BehaviourTest()
that includes functional tests for splango
example.myapp.tests: fixed some docstrings
example.myapp.tests: added functional test for anonymous enrollment "converted" into a registered one.
example.templates.sample: added id attribute for functional test element finding.
added 500.html to get rid of TemplateDoesNotExist message