added some examples

.gitattributes

examples/cdi_read_atts.c

examples/cdi_read_float.c

examples/cdi_read_time.c

examples/cdi_write_const.c

examples/cdi_write_dbl.c

examples/cdi_write_float.c

examples/cdi_write_gribkey.c

examples/cdi_write_pl.c

examples/cdi_write_refgrid.c

examples/cdi_write_refvgrid.c