Toolset 1.9.3 released

[Alex Cabal]

This is a minor release mostly to address issues with images in _Cane_
by Jean Toomer.

This also adds a check in lint to require all heights be specified in vh
units and not percentages.

# 1.9.3

## se build

- Add compatibility code to allow Kindle to display pages whose only
content is an absolutely positioned image

- Replace vh/vw units with percent for compatible epub

## se lint

- Add c-023, font size set without em units

- Add c-024, line-height set with units

- Add c-025, illegal percent unit on height property

## se print-toc

- Fixed a crash when ToC level could not be determined. Thanks to David
Grigg

## se recompose-epub

- recompose-epub: Add `position: relative;` to sections with child
figures that have position: absolute, so that they will position
correctly after recomposition

## se typogrify

- Add word joiners after em dashes within `<cite>` elements