Use the Show instance from Data.NumInstances for functions
rather than defining one locally.

The local definition conflicts in some cases, and prevents compiling.
exprN takes Integer, not Int
Add type signature for expr0.

Both changes are necessary to compile.
Merge pull request #96 from bergey/build-fix

Build fix
Switch (&) to (<>) to avoid deprication warning.
Set version to 0.0.3 (most recent release).

0.0.3 was actualy created on a different branch, but we shouldn't have
development be a lower version...
enable symbolicGetMesh
disable extopenscad
not be moronic
optimize symbolicGetMesh of rotated