Make the book variable width

[jbeckers]

On my 1920x1080 screen, the book is rendered 2546.2 px wide, with a horizontal scroll bar. Resizing firefox makes no change, the book is fixed width.

When printed, the text is illegibly small.

Without display: table rendering is greatly improved:

[jbeckers]

Note that the large width might also be fixed by #105. I'm by no means a css expert. In fact: I have no idea what I'm doing. 😄

[bodewig]

At least for me #105 seems to have fixed the vertical scroll bar. The test of the print version would still be too small for me, but my vision is not the best.

Any chance you could try this again?