diagrams/diagrams-cairo — pull request #34 by bergey (2013-10-06 21:44:44+00:00)
Title: use new pathTrail Iso lens

This patch allows diagrams-cairo to build against diagrams-lib HEAD. I would push this to master myself, except I want to confirm the convention used.

When we switch to lenses and stop exporting constructors, we prohibit the ugly `_pathTrails trs` expression, but also prohibit the pattern match `(Path trs)`. @byorgey, is this what @jeffreyrosenbluth and I should do consistently?