Kompose will read input from stdin

Resolves issue #870

for example,

```
$ cat docker-compose.yaml | kompose convert -f -
INFO Kubernetes file "frontend-service.yaml" created
INFO Kubernetes file "redis-master-service.yaml" created
INFO Kubernetes file "redis-slave-service.yaml" created
INFO Kubernetes file "frontend-deployment.yaml" created
INFO Kubernetes file "redis-master-deployment.yaml" created
INFO Kubernetes file "redis-slave-deployment.yaml" created
```

Added integration test for the same.
`

script/test/cmd/.coverprofile

@@ -0,0 +1 @@
+mode: atomic

script/test/cmd/cmd_test.go

@@ -0,0 +1,30 @@
+package cmd
+
+import (
+	"bytes"
+	"fmt"
+	"io/ioutil"
+	"os"
+	"os/exec"
+	"testing"
+)
+
+var ProjectPath = "$GOPATH/src/github.com/kubernetes/kompose/"
+var BinaryLocation = os.ExpandEnv(ProjectPath + "kompose")
+
+func Test_stdin(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping test in short mode.")
+	}
+	kjson := `{"version": "2","services": {"redis": {"image": "redis:3.0","ports": ["6379"]}}}`
+	cmdStr := fmt.Sprintf("%s convert --stdout -j -f - <<EOF\n%s\nEOF\n", BinaryLocation, kjson)
+	subproc := exec.Command("/bin/sh", "-c", cmdStr)
+	output, err := subproc.Output()
+	if err != nil {
+		fmt.Println("error", err)
+	}
+	g, err := ioutil.ReadFile("/tmp/output-k8s.json")
+	if !bytes.Equal(output, g) {
+		t.Errorf("Test Failed")
+	}
+}

script/test/cmd/tests.sh

@@ -663,5 +663,12 @@ cmd="kompose convert --provider=openshift --stdout -j -f $KOMPOSE_ROOT/examples/
 sed -e "s;%VERSION%;$version;g" -e "s;%CMD%;$cmd;g"  $KOMPOSE_ROOT/script/test/fixtures/examples/output-gitlab-os.json > /tmp/output-os.json
 convert::expect_success_and_warning "kompose convert --provider=openshift --stdout -j -f $KOMPOSE_ROOT/examples/docker-gitlab.yaml" "/tmp/output-os.json"
 
+# Testing stdin feature
+cmd="$KOMPOSE_ROOT/kompose convert --stdout -j -f -"
+sed -e "s;%VERSION%;$version;g" -e "s;%CMD%;$cmd;g"  $KOMPOSE_ROOT/script/test/fixtures/stdin/output.json > /tmp/output-k8s.json
+
+echo -e "\n"
+go test -v github.com/kubernetes/kompose/script/test/cmd
+
 rm /tmp/output-k8s.json /tmp/output-os.json
 exit $EXIT_STATUS