Use CreatedAt/UpdatedAt/StoppedAt from ECS API.

[ejholmes]

Closes #682
Fixes #555

$ emp ps -a acme-inc
v1.web.02510d1a-ca9f-4bda-b9d4-d87e4e3a4b7f  1X  RUNNING  26s  "acme-inc server"
$ # kill task
$ emp ps -a acme-inc
v1.web.b46508ce-0aaf-4100-8192-268d6040182e  1X  RUNNING   2s  "acme-inc server"

Still need to test this. I'm not seeing the new fields returned with the aws CLI.

First commit is the actual changes, second is just godep updates.

Depends on remind101/kinesumer#20

Test

• Log streaming still works.
• stoppedAt/createdAt/startedAt are never nil.

[ejholmes]

Tested this locally. *At fields weren't showing up for me in the CLI originally because of an old version.

[phobologic]

👍 - what's with the new ConfigProvider & session stuff? Is this a change in the SDK that we should be using more regularly?

[ejholmes]

Yeah, v1.0 of the go aws sdk completely changed how you initialize clients.