Feature request: No downgrade flag

[krzysztof-magosa]

Hi.
It would be very handy if there was a flag like --no-downgrade preventing tfupdate from downgrading versions.

Example use case is:

• we have script updating all versions to our current standards/recommendations
• somebody is testing newer version due to issue/bug/whatever

In such case we would like to keep this version as is without changing it.

Thanks.

[casidiablo]

This is such an obvious feature.

I am going to fork for now, and add the feature myself, but this is a must for this tool