Improve usage instructions

Author: fzaninotto

README.md

@@ -8,20 +8,15 @@ Get a full fake GraphQL API with zero coding in less than 30 seconds.
 > I'd love to learn GraphQL, but it seems that I first have to read a book about GraphQL Types and Queries, then install a gazillion npm packages.
 > - About every developer
 
-Start playing with GraphQL right away with `json-graphql-server`, a testing and mocking tool for GraphQL. All it takes is a JSON of your data.
+Start playing with GraphQL right away with `json-graphql-server`, a testing and mocking tool for GraphQL written in Node.js. All it takes is a JSON of your data.
 
 Inspired by the excellent [json-server](https://github.com/typicode/json-server).
 
-## Example
-
-Follow the guide below starting from scratch, or see the example live on StackBlitz:
+## Usage
 
 [![Open in StackBlitz](https://developer.stackblitz.com/img/open_in_stackblitz.svg)](https://stackblitz.com/fork/json-graphql-server)
 
-
-Create a `db.js` file.
-
-Your data file should export an object where the keys are the entity types. The values should be lists of entities, i.e. arrays of value objects with at least an `id` key. For instance:
+Create a `db.js` file that exports an object where the keys are the entity types. The values should be lists of entities, i.e. arrays of value objects with at least an `id` key. For instance:
 
 ```js
 module.exports = {
@@ -40,14 +35,23 @@ module.exports = {
 }
 ```
 
-Start the GraphQL server on localhost, port 3000.
+Use the `npx json-graphql-server <db_file_name>` command to start the GraphQL server on localhost, port 3000.
 
 ```sh
-json-graphql-server db.js
+npx json-graphql-server db.js
 ```
 
-To use a port other than 3000, you can run `json-graphql-server db.js --p <your port here>`
-To use a host other than localhost, you can run `json-graphql-server db.js -h <your host here>` or `--host <your host here>`
+To use a different port, use the `--port` or `-p` option:
+
+```
+npx json-graphql-server db.js --p 8080
+```
+
+To use a different host, use the `--host` or `-h` option: 
+
+```
+npx json-graphql-server db.js -h 127.0.0.1
+```
 
 Now you can query your data in graphql. For instance, to issue the following query:
 
@@ -98,7 +102,7 @@ Note that the server is [GraphiQL](https://github.com/graphql/graphiql) enabled,
 ## Install
 
 ```sh
-npm install -g json-graphql-server
+npm install json-graphql-server
 ```
 
 ## Generated Types and Queries