activation.Files now expect a boolean parameter

The parameter controls if the file should be unset in the environment or not.

More info here: https://github.com/coreos/go-systemd/commit/2b2eff2c24cd57d71edd8c2e22f4e39bd5cf5442#diff-497631d4b782714e9e51170d499b9d97L15
Merge pull request #4 from josevalim/patch-1

activation.Files now expect a boolean parameter