Fix APE6 example for round-tripping

[pllim]

Fix APE6 example for round-tripping, as suggested by @taldcroft (thanks!)

Fix #48

[taldcroft]

The ECSV output needs to be updated to show float64:

# datatype:
# - {name: a, unit: m / s, datatype: int64, format: '%5.2f', description: Column A}
# - name: b
#   datatype: int64
#   meta:
#     column_meta: {a: 1, b: 2}

[pllim]

I updated the output by copying and pasting from my terminal. Good catch, @taldcroft !

[eteq]

LGTM aside from needing to update the "last revised" date. But I did that myself here so, all good!