Merge pull request #3 from mkwidzinska/master

Fix issue with 'server error' when a task description is a blank string
Refactor non-blank directive
Enable user to have more than one list.
Transform app into SPA
Move angular templates to the separate files
Add possibility to create and delete lists
Add name to TaskList
Add migration that fills empty names in existing task lists
Display list name on a list page
Add tests for the list management features.
Destroy associated tasks when deleting a list
Change flash alerts so that they can be closed
Style dashboard and task list
Enable inline editing of a list name
Display the confirmation window when deleting a list
Add error handlers to the TaskList service
Fix Karma tests
Update API documentation