Command set versionning (fix #34)

[antoinealb]

first pull request of the year \o/

This implements command set versionning. I am not entierly sure of my implementation details, especially for the tests, so peer review welcomed.

[msplr]

Why don't you use the COMMAND_SET_VERSION macro/variable for all tests? Isn't it cumbersome to change all tests for every version change?
The rest looks good to me.

[antoinealb]

Well it would change the CRC, so you would have to repair the tests either way. Although the best is probably to compute the CRC automatically.

[msplr]

We should probably add compatibility tests between python and C implementations.
Now we only test each part with itself, which isn't always correct for the actual application.

[antoinealb]

I was thinking about it too, but I don't know if it is worth it. I would do it by making a C to Python binding to the target code and then write all compatibility tests in python.

[msplr]

opened an issue #41 to discuss this topic.

[antoinealb]

It should not be a problem as cmp_read_int handles both signed and unsigned integers (see https://github.com/camgunz/cmp/blob/master/cmp.c#L1202-L1235). I can change it though.

[msplr]

I think this can merge.