simplified feature specs, added more tests and added message for a blank list
refactored controller spec
moved list is empty message into view
make username required and unique, added tests, fixed typo for ajax test
fixed the invalid update spec
added expected error messages
added model tests for username
spec to prevent deleting tasks owned by another user
handles the record not found error
Merge pull request #5 from tienyuan/editing-tests

simplified feature specs, added more tests and added message for a blank...