Initial merge of faas-containerd

This patch completes part of the work in #20 by porting the code
for faas-containerd in-tree. When tested, I was able to deploy
and then remove figlet from the store on `x86_64`.

In a follow-up PR, duplication will be removed where possible
and consolidated with updated documentation.

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

pkg/provider/handlers/replicas.go

@@ -0,0 +1,34 @@
+package handlers
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/containerd/containerd"
+	"github.com/gorilla/mux"
+	"github.com/openfaas/faas-provider/types"
+)
+
+func MakeReplicaReaderHandler(client *containerd.Client) func(w http.ResponseWriter, r *http.Request) {
+
+	return func(w http.ResponseWriter, r *http.Request) {
+		vars := mux.Vars(r)
+		functionName := vars["name"]
+
+		if f, err := GetFunction(client, functionName); err == nil {
+			found := types.FunctionStatus{
+				Name:              functionName,
+				AvailableReplicas: uint64(f.replicas),
+				Replicas:          uint64(f.replicas),
+				Namespace:         f.namespace,
+			}
+
+			functionBytes, _ := json.Marshal(found)
+			w.Header().Set("Content-Type", "application/json")
+			w.WriteHeader(http.StatusOK)
+			w.Write(functionBytes)
+		} else {
+			w.WriteHeader(http.StatusNotFound)
+		}
+	}
+}