fix memory_storage run

- add proper formatting to Readme instructions
- fix docker-compose yaml
- add Enabled flag to admin storage, as without it I saw following error on trying to post a comment:
  ```
  mem_store.r42    | 2020/04/03 15:53:52.433 [INFO]  {logger/logger.go:120 logger.(*Middleware).Handler.func1.1} POST - /cmd - 172.20.0.3 - 200 (25) - 126.8µs - {"method":"admin.enabled","params":"remark","id":29}
  remark42         | 2020/04/03 15:53:52.434 [WARN]  {rest/httperrors.go:85 rest.SendErrorJSON} can't save comment - failed to prepare comment: can't get secret for site remark: site remark disabled - 500 (0) - dev_user/dev_user - /api/v1/comment - [rest/api/rest_private.go:121 api.(*private).createCommentCtrl]
  ```
  Flag was originally added 106c018ef1

backend/_example/memory_store/README.md

@@ -4,10 +4,10 @@
 
 In order to run remark42 with memory_store copy provided `compose-dev-memstore.yml` to the root directory and run:
 
-1. docker-compose -f compose-dev-memstore.yml build
-1. docker-compose -f compose-dev-memstore.yml up
+1. `docker-compose -f compose-dev-memstore.yml build`
+1. `docker-compose -f compose-dev-memstore.yml up`
 
 As usual, demo site will run on http://127.0.0.1:8080/web/
 
-note: in order to work with the latest (current) version of master `go.mod` uses replacement directive for the backend package
-. In real-life usage `replace github.com/umputun/remark/backend => ../../`  should not be used. 
+note: in order to work with the latest (current) version of master `go.mod` uses replacement directive for the backend package.
+In real-life usage `replace github.com/umputun/remark/backend => ../../`  should not be used. 

backend/_example/memory_store/compose-dev-memstore.yml

@@ -7,16 +7,22 @@ services:
 
   remark42:
     build:
-      context: .
+      context: ../../..
       dockerfile: Dockerfile
       args:
         - SKIP_BACKEND_TEST=true
         - SKIP_FRONTEND_TEST=true
     image: umputun/remark42:dev
-    container_name: "remark42"
-    hostname: "remark42"
+    container_name: "remark42-dev"
+    hostname: "remark42-dev"
     restart: always
 
+    logging:
+      driver: json-file
+      options:
+        max-size: "10m"
+        max-file: "5"
+
     ports:
       - "8080:8080" # primary rest server
       - "8084:8084" # local oauth2 server
@@ -36,13 +42,23 @@ services:
       - IMAGE_TYPE=rpc
       - IMAGE_RPC_API=http://mem_store.r42:8080/cmd
 
+    volumes:
+      - ../../../var:/srv/var
+
   mem_store.r42:
     image: umputun/mem_store.r42
     build:
-      context: .
+      context: ../../..
       dockerfile: backend/_example/memory_store/Dockerfile
     container_name: "mem_store.r42"
     hostname: "mem_store.r42"
+
+    logging:
+      driver: json-file
+      options:
+        max-size: "10m"
+        max-file: "5"
+
     environment:
       - API=/cmd
       - SECRET=123456

backend/_example/memory_store/main.go

@@ -55,9 +55,10 @@ func main() {
 	srv := server.NewRPC(dataStore, adminStore, imgStore, &rpcServer)
 
 	admRec := accessor.AdminRec{
-		SiteID: "remark",
-		IDs:    []string{"dev_user"},
-		Email:  "admin@example.com",
+		SiteID:  "remark",
+		Enabled: true,
+		IDs:     []string{"dev_user"},
+		Email:   "admin@example.com",
 	}
 	adminStore.Set("remark", admRec)