Update getting_started.md
Update getting_started.md

Hello World example at the main Readme file (https://github.com/channelcat/sanic/blob/master/README.rst) is different, it returns json. Here is returned text. In the following examples, such as Routing (http://sanic.readthedocs.io/en/latest/sanic/routing.html) is again used json. Therefore I suggest to make examples the same, having json as output
ashleysommer/sanic,lixxu/sanic,ashleysommer/sanic,yunstanford/sanic,channelcat/sanic,lixxu/sanic,channelcat/sanic,yunstanford/sanic,lixxu/sanic,yunstanford/sanic,yunstanford/sanic,ashleysommer/sanic,channelcat/sanic,channelcat/sanic,lixxu/sanic