- updated topo functions to read directly from
  srtm30+ or etopo1 binary files (the int16
  ones) -- see the Notes on which files to
  download and put on your path
- updated topo functions to get topo data
  from CrustX.X using getcrust
- updated topo_colormap to take an axes
  input and allow outputting colormaps
  with less than 64 colors