Draft: Implement nesting on threads
This is an attempt to implement nesting in order to make a reply to a status appear nested on its parent.
To do:
- Create the vertical lines;
- Decide on a nesting limit. I think two or three nested statuses seems reasonable but I'm still not sure how to represent the further nested statuses;
- Once we decide on a nesting limit, change the new class names accordingly. The current names are only placeholders.
This commit passed all tests and I haven't found anything broken yet. Still, if you find any bugs or problems (or have any suggestions) please let me know.
This commit is related to issue #387.