TODO
1 Setters for has many associations:
# project.tasks << new_nask
Impediment: has_many association doesn't know how current entity named in collections.
For example: GeneralUser has_many Assignables, but Assignable doesn't have any
GeneralUser directly - Assignable belongs to GeneralUser as owner.
2 (Need to discuss) belongs_to associations setters works fine when called on entity:
# task.owner = general_user
# task.save
But we still can not pass entity inside #new:
# task = TargetProcess::Task.new(name: "aaa", project: tp_project_instance)
# task.save #=> Error
3 Update README