Update the readme.md file

Author: alexcanessa

README.md

@@ -1,2 +1,20 @@
 # github-release-notes
 Node module to publish release notes based on commits between the last two tags.
+
+## Installation
+
+Install `github-release-notes` via npm:
+
+```
+npm install github-release-notes --save-dev
+```
+
+## Usage
+
+- You can run the command via the terminal (the three arguments ar all required):
+
+```
+node github-release-notes --token=[token] --username=[username] --repo=[repo name]
+```
+
+To generate a github token, follow [this link](https://help.github.com/articles/creating-an-access-token-for-command-line-use/);