Variadic templates FTW
Added an extra field for attaching files to tasks.
Fix syntax for displaying attachments as a string.
Implement adding and removing attachments via the attach and detach commands.
Fix wrong test result.
Merge pull request #292 from lowjoel/attachment-parsing

Attachment parsing
Implemented dependency highlighting.
Lints
Added constants.
Highlight dependencies, test fixes
Refactoring of task columns
Fixed lints.