Dereference `Flag`s if they are pointers
Dereference `Flag`s if they are pointers

When checking if environment variables are set.

We don't support pointer flags currently (though this is the default in
the `v2` branch), but this fixes #516

codegangsta/cli,urfave/cli,urfave/cli,murdinc/cli,murdinc/cli,pjvds/cli,minio/cli,murdinc/cli,phinnaeus/cli,codegangsta/cli,pjvds/cli,phinnaeus/cli,pjvds/cli,phinnaeus/cli,minio/cli,minio/cli