Added tests for pycomber.manager.Manager __init__, set_factory and get_factory
Fixed comment
Added tests for pycomber.manager.Manager: set_strategy() and get_strategy()
Refactored pycomber.manager.Manager.set_factory() so it wil not require base_type to be covered by strategy
Test behaviour of given strategy and factory
Added tests for pycomber.manager.Manager.__call__
Added tests for pycomber.merger
Fixed tests for pycomber.manager.Manager
Fixed pycomber.strategies and tests for Python3