Dockerfile and addition of optional commands

[trstickland]

• Adds a Dockerfile
• Script now accepts a command, gffmunger [options] [command], that defines action to take; currently has only one function, to move annotations from polypeptide to mRNA (or other parent), and defaults to this if no command is specified. So ATM there's no extra functionality, but it provides a framework for adding new commands that invoke functions.

[puethe]

Looks good!
I'd recommend adding minimum versions for your dependencies in setup.py.

[trstickland]

Interesting question about dependencies. I've only tested with up to date versions, but have no reason to think old versions won't work. If I make the current version as a requirement, it prevents an install with older versions (and potentially introduces a conflict) when that may be unnecessary :-/

[puethe]

It's your decision in the end. I just noticed it as I had to recently raise the pyyaml version in chado-tools as some functionality I use was only added in in version 5 or so.

[trstickland]

could do with syntax for "warn user package version hasn't been tested if < n" ;)