New features:
- The solver now supports masks. Masks are a parallel array, like weights. They tell the solver to ignore masked-out slots from the solution. Masked-out slots will not be observed, propagated-from, or propagated-into (similarly like the cuboid boundary is not propagated into). See PR #29 for more.
Internal changes:
- Rng now implements Clone.
- C bindings are now generated automatically during build.