[JAVA-Spring-Server] README.md points to a wrong URL.

Description

There are two problems with README:

1. The class to use is not named. It is the Swagger2SpringBoot

2. The path to access is not necessarily /. It might be affected by what is configured in the openapi.yaml

Swagger-codegen version

swagger-codegen-cli-3.0.0-20180717.153005-90

Swagger declaration file content

openapi: 3.0.0
servers:
  - url: 'http://localhost:8080/v1'
info:
  version: 0.0.0
  title: Example
paths:
  /randomPet:
    get:
      responses:
        '200':
          description: Random pet
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Pet'
components:
  schemas:
    Pet:
      type: object
      required:
        - petType
      properties:
        petType:
          type: string

Generated README.md

# Swagger generated server

Spring Boot Server 


## Overview  
This server was generated by the [swagger-codegen](https://github.com/swagger-api/swagger-codegen) project.  
By using the [OpenAPI-Spec](https://github.com/swagger-api/swagger-core), you can easily generate a server stub.  
This is an example of building a swagger-enabled server in Java using the SpringBoot framework.  

The underlying library integrating swagger to SpringBoot is [springfox](https://github.com/springfox/springfox)  

Start your server as an simple java application  

You can view the api documentation in swagger-ui by pointing to  
http://localhost:8080/  

Change default port value in application.properties

Expected

1. The "start your server" is more verbose.
2. The URL is correct.
3. The advice to check the application.properties is more prominent.

For example:

# Swagger generated server

Spring Boot Server 


## Overview  
This server was generated by the [swagger-codegen](https://github.com/swagger-api/swagger-codegen) project.  
By using the [OpenAPI-Spec](https://github.com/swagger-api/swagger-core), you can easily generate a server stub.  
This is an example of building a swagger-enabled server in Java using the SpringBoot framework.  

The underlying library integrating swagger to SpringBoot is [springfox](https://github.com/springfox/springfox)  

1. Adjust your applications settings in src/main/resources/application.properties
2. Start your server (class io.swagger.Swagger2SpringBoot) as a simple java application  

You can view the api documentation in swagger-ui by pointing to  
http://localhost:8080/v1/