added clipTo
added clipped and mdified clipTo not to set the trace
Another attempt at a proper intersection Trace in clipTo
Fix variable shadowing
Merge branch 'master' into clipTo
Trace of intersections, using new SortedList Trace
haddock: fix typo
clipTo test (Trace of intersections)

jeffryrosenbluth's test design
I added arrows to the graphical output
-Wall: don't import Data.Monoid.Inf
-Wall: remove unneeded imports
Merge branch 'master' into clipTo
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Merge pull request #144 from diagrams/clipTo

add several clipping functions which set Envelope and Trace