Fig compatibility layer 649

TODO deal with port edge cases, e.g. just container port specified, or IP and port specified on host
See http://www.fig.sh/yml.html
Issues have been raised for this missing functionality, which is not yet supported by Flocker.

Fixes #649
You should choose pairs of numbers that are different, so that your test ensures the external/internal parsing is done correctly. As it is it might be buggy but your test won't notice because both values are identical.