Create changelog based on pull requests

I created a simple tool here https://github.com/lalitkapoor/github-changes.

To install it:
`npm install -g github-changes`

This was the command used to generate the changelog:
`github-changes -o linkedin -r dustjs -a -v`

Please let me know if you need any help adding it to your release script. If there are any improvements you'd like to see in this tool please feel free to open an issue :) Thanks!