Added test for gravmag.polyprism comparing with gravmag.prism
Made gridder.cut return a slice of the arrays instead of a copy
Bug fix in mesher.TesseroidMesh: dims was giving negative dz
Revert "Bug fix in mesher.TesseroidMesh: dims was giving negative dz"

This reverts commit a666b292bbb5e2cb20967510bc6bc7c3e401fc2b.
Added numpy include dirs in setup for windows compilation
Merge branch 'master' into devel