Tag image managment

[baptistedonaux]

I use Fig to deploy an application but I would like build images to stay in a history of my last builds. I think at an possibility to tag the image created by fig.

Per example, for a project X, I have two service Y and Z. The two images created will be x_y_1:latest and x_z_1:latest. It will be possible to add an option to build and run images with others tags ?

Example :
fig --tag v1.0 build
fig --tag v1.0 up

[dnephin]

I believe this is related to #457 and #213

Which would support versions by using environment variables.