Fix missing environment variables in spawned pod when using VariableKubeSpawner

[xeliba]

This explictly injects the environment variables in user_options['environment'] and therefore fixes #77

[danlester]

Thank you so much for sharing this with us.

As discussed, it's not "supposed" to work like this in the normal case, so I don't think it makes sense to merge this into the main codebase until we really understand what's different in your situation.

If others are reading this and also believe this branch works for them, please let us know!

[aberey]

I have the exact same issue (#77) and the change in this pull request fixed the issue for me.