Summary:
- Add 'make verify' to Travis.
- Fix verify-golint.sh: old invocation would not work unless GOPATH is a
single directory.
- Fix verify-govet.go: 'go vet' does not take flags, should use 'go tool
vet'.
- Fix early termination of hack/verify-govet.sh.
- Enable 'go vet' in 'make verify'; will prevent introducing problems
detected by the vet tool in future PRs.
- Make sure golint is installed in Travis.
- Improve install-tools.sh, parity with the one in openshift/origin.
- s/os::util::sed/s2i::util::sed for consistency.
- Reimplement/simplify find_files, now called s2i::util::find_files, and
use it in all scripts consistently.
- Suggest autocorrection for gofmt, as seen in openshift/origin.
- Do not check Go version (verify-*.sh should be run no matter the Go
version?!).
- Do not create directory _output/govet (not used?!).
- Explicitly disable check of composite literals. Vet gives false
positives on literals using unkeyed fields.
