fleet: add build-docker script

Allows the user to build fleet from inside a container
debug: add MarshalJSON to UnitStateGenerator
Merge pull request #894 from bcwaldon/dump-usGen

debug: add MarshalJSON to UnitStateGenerator
fleetctl: introduce stderr/stdout helpers
fleetctl: use stderr where appropriate
Merge pull request #899 from bcwaldon/fleetctl-print

Use simple helpers for printing from fleetctl
examples: warn about detached mode
Merge pull request #901 from robszumski/docs-detached-mode

examples: warn about detached mode
Merge pull request #889 from bacongobbler/build-docker

fleet: add build-docker script
README: bump required go version to 1.3+
Merge pull request #905 from bcwaldon/go-version

README: bump required go version to 1.3+
bump: github.com/godbus/dbus
bump: github.com/coreos/go-systemd
Merge pull request #908 from bcwaldon/bumpit

bump github.com/godbus/dbus and github.com/coreos/go-systemd/*
fleetctl: only call API once in status command
fleetctl: check for global units in status command
fleetctl: check for global units in journal command
fleetctl: bubble up errors from ssh command
fleetctl: check for global units in ssh command
Merge pull request #911 from bcwaldon/895

Fail on global units in fleetctl commands