solved problem with test_netcdf

Hi Shyue, 

the problem with the netcdf test is hopefully solved in this revision. I was trying to support both scipy.io.netcdf as well as netcdf4 although the two APIs are not 100% compatible. netcdf4 is more flexible that the interface provided by scipy that only supports netcdf3. Now the test is skipped if netcdf4 is not available. Future versions of abinitio will require netcdf4