Add a README to the client's package…

… taken from the old engine-api project.

Signed-off-by: Vincent Demeester <vincent@sbr.pm>

README.md

@@ -0,0 +1,37 @@
+## Client
+
+The client package implements a fully featured http client to interact with the Docker engine. It's modeled after the requirements of the Docker engine CLI, but it can also serve other purposes.
+
+### Usage
+
+You can use this client package in your applications by creating a new client object. Then use that object to execute operations against the remote server. Follow the example below to see how to list all the containers running in a Docker engine host:
+
+```go
+package main
+
+import (
+	"fmt"
+
+	"github.com/docker/docker/client"
+	"github.com/docker/docker/api/types"
+	"golang.org/x/net/context"
+)
+
+func main() {
+	defaultHeaders := map[string]string{"User-Agent": "engine-api-cli-1.0"}
+	cli, err := client.NewClient("unix:///var/run/docker.sock", "v1.22", nil, defaultHeaders)
+	if err != nil {
+		panic(err)
+	}
+
+	options := types.ContainerListOptions{All: true}
+	containers, err := cli.ContainerList(context.Background(), options)
+	if err != nil {
+		panic(err)
+	}
+
+	for _, c := range containers {
+		fmt.Println(c.ID)
+	}
+}
+```