Use go-uuid instead of "uuidgen" command based implementation

I think it's better to use [go-uuid](https://code.google.com/p/go-uuid/) than "uuidgen" command based implementation.  Besides, go-uuid is used in [kubernetes](https://github.com/GoogleCloudPlatform/kubernetes/blob/master/Godeps/Godeps.json#L8-L12).  

However, I have one problem...  I know I have to add go-uuid to `Godep.json`.  But, `godep save ./...` fails in my environment.  I'm not sure why...  I would be very appreciated if somebody helped me finalize this PR.

```
$ go version
go version go1.3 darwin/amd64

$ go env
GOARCH="amd64"
GOBIN=""
GOCHAR="6"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/shingo/go:/Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/third_party"
GORACE=""
GOROOT="/usr/local/opt/go/libexec"
GOTOOLDIR="/usr/local/opt/go/libexec/pkg/tool/darwin_amd64"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fno-common"
CXX="clang++"
CGO_ENABLED="1"

$ pwd
/Users/shingo/go/src/github.com/everpeace/kubernetes-mesos

$ godep save ./...
godep: cannot find package "github.com/GoogleCloudPlatform/kubernetes/pkg/registry/controller" in any of:
        /usr/local/opt/go/libexec/src/pkg/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/controller (from $GOROOT)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/controller (from $GOPATH)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/third_party/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/controller
godep: cannot find package "github.com/GoogleCloudPlatform/kubernetes/pkg/registry/endpoint" in any of:
        /usr/local/opt/go/libexec/src/pkg/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/endpoint (from $GOROOT)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/endpoint (from $GOPATH)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/third_party/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/endpoint
godep: cannot find package "github.com/GoogleCloudPlatform/kubernetes/pkg/registry/etcd" in any of:
        /usr/local/opt/go/libexec/src/pkg/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/etcd (from $GOROOT)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/etcd (from $GOPATH)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/third_party/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/etcd
godep: cannot find package "github.com/GoogleCloudPlatform/kubernetes/pkg/registry/memory" in any of:
        /usr/local/opt/go/libexec/src/pkg/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/memory (from $GOROOT)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/memory (from $GOPATH)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/third_party/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/memory
godep: cannot find package "github.com/GoogleCloudPlatform/kubernetes/pkg/registry/minion" in any of:
        /usr/local/opt/go/libexec/src/pkg/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/minion (from $GOROOT)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/minion (from $GOPATH)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/third_party/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/minion
godep: cannot find package "github.com/GoogleCloudPlatform/kubernetes/pkg/registry/pod" in any of:
        /usr/local/opt/go/libexec/src/pkg/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/pod (from $GOROOT)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/pod (from $GOPATH)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/third_party/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/pod
godep: cannot find package "github.com/GoogleCloudPlatform/kubernetes/pkg/registry/service" in any of:
        /usr/local/opt/go/libexec/src/pkg/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/service (from $GOROOT)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/service (from $GOPATH)
        /Users/shingo/go/src/github.com/GoogleCloudPlatform/kubernetes/third_party/src/github.com/GoogleCloudPlatform/kubernetes/pkg/registry/service
godep: error loading dependencies
```