#15 first draft of DataSource class
#15 renamed MasterViewController -> TasksViewController
#15 added a few specs for DataSource
#15 added more unit tests for DataSource
#15 minor tidy to DataSourceSpec
#15 further tests for DataSource
#15 basic specs for TasksViewController
#15 further refinements to unit testing view controllers
Merge pull request #16 from jbrunton/dev-15-unit-test-ui

Merge dev-15-unit-test-ui fixes #15