[Roadster] sexy rivers

[Ian McIntosh]

Rivers in Roadster should look this nice:

http://maps.google.com/maps?ll=37.780280,-121.402874&spn=0.014951,0.023646&hl=en

...even when we're provided with low point-count rivers like the one
near the bottom in this screenshot:

http://linuxadvocate.org/projects/roadster/images/roadster-0.2.7-1_large.png

Anyone want to figure out a good way to do it?

A similar challenge exists for lakes.

-Ian