rename config.example to config.template and fix readme

README.md

@@ -3,13 +3,19 @@
 [ ![Codeship Status for koodiklinikka/koodiklinikka.fi-api](https://codeship.com/projects/5ba71cf0-7f0a-0132-b32d-661179cb74c9/status?branch=master)](https://codeship.com/projects/57155)
 
 ### Start developing
-* Install node.js
+* Install node.js & install dependencies
 ```
 $ git clone git@github.com:koodiklinikka/koodiklinikka.fi-api.git
 $ cd koodiklinikka.fi-api
 $ npm install
 ```
 
+-* Create `config.json` file. See [config.template.json](https://github.com/koodiklinikka/koodiklinikka.fi-api/blob/master/config.template.json) for possible options.
+-The config file consists of environment specific blocks. Environment variable `NODE_ENV` determines which block is used. If the environment variable is not present, the `development` block will be selected.
+-`all` block is always used and the block selected is merged into it so that it overwrites the values defined in it.
+
+### Run development environment
+
 * ``` $ npm start ```
 
 Now app will be running on `localhost:9000`.