Fixture Proof010.json open to Interpretation

[roblesjoel]

In the fixture proof010.json, there are two identical disclosed indexes.
For me that also means that in the disclosed messages vector, the same message is present twice.
There is no check for that.
The only check is if the length of the disclosed messages is the same as the length of the disclosed indexes.

Other implementations (see Greg Bernstein's JS implementation) solve this issue by filtering the fixture messages, so that the messages only appears once in the vector.
In that case the lengths of the disclosed messages and indexes would mismatch.

There should be a check if the disclosed indexes are in order, and maybe a check if there are duplicate entries in the vectors.