KUBE_EXTRA_GOPATH to append to the GOPATH

So you can add your own package to the GOPATH outside of the kube tree
KUBE_NO_GODEPS to not use in tree godeps

If this is set, and it normally shouldn't be, the config file will not
add the in tree Godeps to the GOPATH.  So all of them must be solved by
the KUBE_EXTRA_GOPATH
Merge pull request #1260 from eparis/config-gopath-overrides

Config gopath overrides