Modify rectangle-based visibility detection so it supports vertical writing mode.
Attempt at fixing findPageByRectangles for vertical writing mode
Second attempt at fixing findPageByRectangles for vertical writing mode
(works but confused about the requirement of RTL checks)
Remove disabled code for RTL handling when in VWM.
Special handling of RTL is not needed in this case.
adjusted CSS column algorithm in reflowable view to take into account single-column vertical writing mode (user setting has no effect, max text width corresponds  2x single-column threshold)
Merge pull request #113 from readium/feature/vertical-writing-client-rects

Visibility computations by client rectangles, vertical writing mode (column layout) #87