Version 0.3 of vu.

Bumped the version numbering back to beta 0.3 to indicate that there has
been, and likely will continue to be, major code changes. Reorganization
and refactoring of the existing code base centered on vu and vu/render
packages. New bits added include:
  o vu/land  - height map and landscape generator.
  o vu/panel - experimental 2D control overlays for 3D apps.
  o animated model example with IQM importer.
  o particle example.
  o ray-cast example.
  o updated to go 1.3.