UIStackView internal constraints all have a required priority, so adding
the image constrain in TimelineStatusTableViewCell.awakeFromNib caused
an unsatisfiable constraint. Fixed by replicating the UISV constraints
manually, with the constrain on the leading edge of the first button
being made a placeholder.
The stack view hiding constraint sets the height to 0 with a priority of
999.999, so the priority 1000 aspect ratio constraint was causing an
error and making the container view still have a height. Setting the
priority to 999 resolves the issue.
UITextView uses TextKit internally, unlike UILabel, so no additional
code is needed to keep the TextKit and view representations of the text
in sync since they are one and the same. This means that detecting which
character was tapped in a content text view is much more accurate, which
means link handling is substantially imrpoved.
Fixes#20