support `--save` to append installed package to requirements.txt?

[bukuta]

Thanks for this great project.

Any idea to support cget install with --save option?

It may be quite convenient to trace dependences , or we should edit the requirements.txt especially.

[pfultz2]

Any idea to support cget install with --save option?

This means it would install the dependency and add it to the requirements.txt list?

I think thats very doable.