Set assignee status after assignee

It is illegal to set the status for a task without an assignee, and
setting the assignee clears it so we do so afterwards.
Fix existing tests to match new assignee behavior
Merge commit 'f6e81c65c0623afaf186608c6080ec49ef4523de' into set-assignee-status

Conflicts:
	lib/asana_export_importer/models/Task.js
	test/integration.js
Remove assignee_status from expected output of a test
Add tests for setting assignee status
Merge pull request #19 from Asana/set-assignee-status

Set assignee status after assignee