Have gx-go rw install missing packages

[aschmahmann]

Developers may want to change their dependencies (e.g. in the package.json file) and when they perform a gx-go rw will see their imports rewritten. However, unless they also run gx install their code will not be functional. It may be worth have gx-go rw call gx install.

[lanzafame]

I think this would be better solved by a shell alias/script that you define yourself, that does a gx install before gx-go rw, instead changing the way gx-go rw works internally.