return list of traces
SortedList
minor changes to merge
fixed comment
use op
updates to SortedList

  * Remove Wrapped instance.  Part of the point is that SortedList a
    is NOT isomorphic to [a].
  * Add smart constructor, accessor, and some mapping functions
  * other misc refactorings
D.C.Trace: some documentation improvements
D.C.Trace: more documentation improvements
improve getRayTrace documentation, and don't export it from Diagrams.Core
D.C.Trace: more Haddock improvements
change bird tracks to @ in preparation for adding diagrams-haddock images
ignore .diagrams-cache
diagrams-haddock illustrations for D.C.Trace
add extra-doc-files to .cabal
Merge pull request #48 from diagrams/traces

return list of traces
Help lens along finding Wrapped instance

lens-3.8 is less good at finding a suitable instance
using wrapped' or unwrapped', which have narrower types
(compare Iso', Iso) than the unprimed versions, works
cabal: bump lower bounds of dependencies

closes #49
Update change long to include change to trace
remvoe 1.x
Merge branch 'master' into units
master -> units