[cairo] Better Examples of Cairo Operators

[Lawrence D'Oliveiro]

I’ve decided that the current page
<http://cairographics.org/operators/> doesn’t really do a good job of
showing off the differences between the various Cairo drawing
operators. So I have reworked my Qahirah example script
<https://github.com/ldo/qahirah_examples/blob/master/operators>, which
previously recreated the exact images on this page, to use more
elaborate gradient fill patterns instead.

You can see what the new output looks like here
<http://default-cube.deviantart.com/art/Operators-520466116>.