Text along path

In order to set text along a given path, you can use the `curvedtext()`
decorator. The example shows a few useful parameter settings for this
decorator.

! To output just the curved text, but not the path, you can use the
draw method of the canvas instead of the stroke method. By that the
path is omitted in the output completely. In contrast, if you set the
linewidth to zero instead, the path will still be visible, as those
lines will be rendered as the thinnest available linewidth on the
output device according to the PostScript and PDF specification.
