Update dependency reference

[DorfilIkatu]

github.com/codegangsta/cli has moved to gopkg.in/urfave/cli.v1. Github is automatically redirecting requests to codegangsta, but it is recommended to update the references.

[brikis98]

LGTM, thx! How did you test this change?

[DorfilIkatu]

I'm adding the fetch tool to a SDK using Yocto. I was already able to build fetch and it's dependencies. But I realize I was having two dependencies that had exactly the same source code (github.com/codegangsta/cli and gopkg.in/urfave/cli.v1).
What happened was that fetch imports github.com/codegangsta/cli which is redirected to gopkg.in/urfave/cli.v1, and gopkg.in/urfave/cli.v1 was importing itself (https://github.com/urfave/cli/blob/934abfb2f102315b5794e15ebc7949e4ca253920/altsrc/flag.go#L9), so I ended up with the both dependencies.
After making the change, fetch tool stills builds correctly and I can use it with no problems in my SDK.

[brikis98]

OK, great, thanks. I'll merge and let the tests run. If they pass, I'll create a new release and paste the link.

[brikis98]

https://github.com/gruntwork-io/fetch/releases/tag/v0.3.2