[skip ci] Updated the document of examples/echo (#646)

* [skip ci] Updated the document of examples/echo

A few params seems to be incorrect.

* Undo the changes of docker tag command

* Use fn instead of docker command

Author: kunihiko-t

examples/echo/README.md

@@ -2,37 +2,18 @@
 
 This images compares the payload info with the header.
 
-## Requirements
-
-- IronFunctions API
-
-## Development
-
-### Building image locally
-
-```
-# SET BELOW TO YOUR DOCKER HUB USERNAME
-USERNAME=YOUR_DOCKER_HUB_USERNAME
-
-# build it
-./build.sh
 ```
-
-### Publishing to DockerHub
-
-```
-# tagging
-docker run --rm -v "$PWD":/app treeder/bump patch
-docker tag $USERNAME/func-echo:latest $USERNAME/func-echo:`cat VERSION`
-
-# pushing to docker hub
-docker push $USERNAME/func-echo
-```
-
-### Testing image
-
-```
-./test.sh
+# Create your func.yaml file
+fn init <YOUR_DOCKERHUB_USERNAME>/func-echo
+# Build the function
+fn build
+# Test it
+echo '{"input": "yoooo"}' | fn run
+# Push it to Docker Hub
+fn push
+# Create routes to this function on IronFunctions
+fn apps create <YOUR_APP>
+fn routes create <YOUR_APP> /echo
 ```
 
 ## Running it on IronFunctions
@@ -41,37 +22,17 @@ docker push $USERNAME/func-echo
 
 ```
 # Set your Function server address
-# Eg. 127.0.0.1:8080
+# Eg. 
+# FUNCAPI=127.0.0.1:8080
+# APPNAME=echo
 FUNCAPI=YOUR_FUNCTIONS_ADDRESS
+APPNAME=YOUR_APP
 ```
 
-### Running with IronFunctions
-
-With this command we are going to create an application with name `echo`.
-
-```
-curl -X POST --data '{
-    "app": {
-        "name": "echo",
-    }
-}' http://$FUNCAPI/v1/apps
-```
-
-Now, we can create our route
-
-```
-curl -X POST --data '{
-    "route": {
-        "image": "'$USERNAME'/func-echo",
-        "path": "/echo",
-    }
-}' http://$FUNCAPI/v1/apps/echo/routes
-```
-
-#### Testing function
+### Testing function
 
 Now that we created our IronFunction route, let's test our new route
 
 ```
-curl -X POST --data '{"input": "yoooo"}' http://$FUNCAPI/r/echo/echo
+curl -X POST --data '{"input": "yoooo"}' http://$FUNCAPI/r/$APPNAME/echo
 ```