Merge branch 'fix-docs-for-field' into placeholder
Added GEBCO netCDF reader.

Added
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* Read a RasterModelGrid from a gebco netCDF file. Thus far, this has
  only been tested on a single gebco file. It definitely needs some more
  testing.
Merge branch 'add-gebco-netcdf' of github.com:mcflugen/landlab into add-gebco-netcdf
Merge pull request #52 from mcflugen/add-gebco-netcdf

Added read support for GEBCO netCDF.