replace godep with glide

[ericchiang]

Please review the first commit which updates the documentation and adds the glide files.

The second commit is huge as glide does not remove _test.go files and testdata.

See coreos/docs#775 for discussion.

Closes #387

[chancez]

@ericchiang We can use https://github.com/sgotti/glide-vc to remove some things (we can't use only-go because it will strip files needed by cgo), but it would help with test files, and packages which are not part of the direct import-tree.

[ericchiang]

Just to follow up from outside discussions. We like glide-vc but don't like adding an additional dependency in order to work with the vendor directory. If this is functionality is important then glide should implement it or we should consider a different tool.

There's some discussion here Masterminds/glide#166

[ericchiang]

I'd also like to note that I'm fine with glide not removing unused sub-packages.

[bobbyrullo]

how does one do the equivalent of godep go {build|test} ?

[ericchiang]

Ensure you have either Go 1.6 or Go 1.5 with GO15VENDOREXPERIMENT=1. Then just use the go tool. Since glide puts everything in ./vendor all dex code will build using that directory.

[bobbyrullo]

LGTM

[sym3tri]

🎉